Web Development Chapter 8 (JavaScript)

Réussis tes devoirs et examens dès maintenant avec Quizwiz!

Update the myDog object's name property. Let's change her name from "Coder" to "Happy Coder". You can use either dot or bracket notation. // Example var ourDog = { "name": "Camper", "legs": 4, "tails": 1, "friends": ["everything!"] }; ourDog.name = "Happy Camper"; // Setup var myDog = { "name": "Coder", "legs": 4, "tails": 1, "friends": ["freeCodeCamp Campers"] }; // Only change code below this line. myDog.name = "Happy Coder"; Update myDog's "name" property to equal "Happy Coder". Passed Do not edit the myDog definition

After you've created a JavaScript object, you can update its properties at any time just like you would update any other variable. You can use either dot or bracket notation to update. For example, let's look at ourDog: var ourDog = { "name": "Camper", "legs": 4, "tails": 1, "friends": ["everything!"] }; Since he's a particularly happy dog, let's change his name to "Happy Camper". Here's how we update his object's name property: ourDog.name = "Happy Camper"; or ourDog["name"] = "Happy Camper"; Now when we evaluate ourDog.name, instead of getting "Camper", we'll get his new name, "Happy Camper".

Use bracket notation to find the first character in the lastName variable and assign it to firstLetterOfLastName. Hint Try looking at the firstLetterOfFirstName variable declaration if you get stuck. // Example var firstLetterOfFirstName = ""; var firstName = "Ada"; firstLetterOfFirstName = firstName[0]; // Setup var firstLetterOfLastName = ""; var lastName = "Lovelace"; // Only change code below this line firstLetterOfLastName = lastName; firstLetterOfLastName = lastName[0]; The firstLetterOfLastName variable should have the value of L. Passed You should use bracket notation.

Bracket notation is a way to get a character at a specific index within a string. Most modern programming languages, like JavaScript, don't start counting at 1 like humans do. They start at 0. This is referred to as Zero-based indexing. For example, the character at index 0 in the word "Charles" is "C". So if var firstName = "Charles", you can get the value of the first letter of the string by using firstName[0].

There should be at least 5 sub-arrays in the list. var myList = [ ["Carrot", 7], ["Apple", 3], ["Orange", 2], ["Lemon", 5], ["Lime", 7] ]; myList should be an array Passed The first elements in each of your sub-arrays must all be strings Passed The second elements in each of your sub-arrays must all be numbers Passed You must have at least 5 items in your list.

Create a shopping list in the variable myList. The list should be a multi-dimensional array containing several sub-arrays. The first element in each sub-array should contain a string with the name of the item. The second element should be a number representing the quantity i.e. ["Chocolate Bar", 15]

Build myStr from the strings "This is the start. " and "This is the end." using the + operator. // Example var ourStr = "I come first. " + "I come second."; // Only change code below this line var myStr= "This is the start." + " This is the end."; myStr should have a value of This is the start. This is the end. Passed Use the + operator to build myStr Passed myStr should be created using the var keyword. Passed Make sure to assign the result to the myStr variable.

In JavaScript, when the + operator is used with a String value, it is called the concatenation operator. You can build a new string out of other strings by concatenating them together. Example 'My name is Alan,' + ' I concatenate.' Note Watch out for spaces. Concatenation does not add spaces between concatenated strings, so you'll need to add them yourself.

Change the 0.0 so that product will equal 5.0 var product = 2.0 * 2.5;

In JavaScript, you can also perform calculations with decimal numbers, just like whole numbers. Let's multiply two decimals together to get their product.

Build myStr over several lines by concatenating these two strings: "This is the first sentence. " and "This is the second sentence." using the += operator. Use the += operator similar to how it is shown in the editor. Start by assigning the first string to myStr, then add on the second string. // Example var ourStr = "I come first. "; ourStr += "I come second."; // Only change code below this line var myStr = "This is the first sentence. "; myStr += "This is the second sentence."; myStr should have a value of This is the first sentence. This is the second sentence. Passed Use the += operator to build myStr

We can also use the += operator to concatenate a string onto the end of an existing string variable. This can be very helpful to break a long string over several lines. Note Watch out for spaces. Concatenation does not add spaces between concatenated strings, so you'll need to add them yourself.

Create a function timesFive that accepts one argument, multiplies it by 5, and returns the new value. See the last line in the editor for an example of how you can test your timesFive function. // Example function minusSeven(num) { return num - 7; } // Only change code below this line function timesFive(param1) { return param1 *5; } console.log(minusSeven(10)); timesFive should be a function Passed timesFive(5) should return 25 Passed timesFive(2) should return 10 Passed timesFive(0) should return 0

We can pass values into a function with arguments. You can use a return statement to send a value back out of a function. Example function plusThree(num) { return num + 3; } var answer = plusThree(5); // 8 plusThree takes an argument for num and returns a value equal to num + 3.

Create a variable myDecimal and give it a decimal value with a fractional part (e.g. 5.7). var ourDecimal = 5.7; // Only change code below this line var myDecimal= 5.7;

We can store decimal numbers in variables too. Decimal numbers are sometimes referred to as floating point numbers or floats. Note Not all real numbers can accurately be represented in floating point. This can lead to rounding errors. Details Here.

In this challenge, we provide you with a noun, a verb, an adjective and an adverb. You need to form a complete sentence using words of your choice, along with the words we provide. You will need to use the string concatenation operator + to build a new string, using the provided variables: myNoun, myAdjective, myVerb, and myAdverb. You will then assign the formed string to the result variable. You will also need to account for spaces in your string, so that the final sentence has spaces between all the words. The result should be a complete sentence. function wordBlanks(myNoun, myAdjective, myVerb, myAdverb) { // Your code below this line var result = "The " + myNoun + " was " + myAdjective + " and " + myVerb + " very " + myAdverb; // Your code above this line return result; } // Change the words here to test your function wordBlanks("dog", "big", "ran", "quickly"); wordBlanks("","","","") should return a string. Passed wordBlanks("dog", "big", "ran", "quickly") should contain all of the passed in words separated by non-word characters (and any additional words in your madlib). Passed wordBlanks("cat", "little", "hit", "slowly") should contain all of the passed in words separated by non-word characters (and any additional words in your madlib).

We will now use our knowledge of strings to build a "Mad Libs" style word game we're calling "Word Blanks". You will create an (optionally humorous) "Fill in the Blanks" style sentence. In a "Mad Libs" game, you are provided sentences with some missing words, like nouns, verbs, adjectives and adverbs. You then fill in the missing pieces with words of your choice in a way that the completed sentence makes sense. Consider this sentence - "It was really ____, and we ____ ourselves ____". This sentence has three missing pieces- an adjective, a verb and an adverb, and we can add words of our choice to complete it. We can then assign the completed sentence to a variable as follows: var sentence = "It was really" + "hot" + ", and we" + "laughed" + "ourselves" + "silly.";

Initialize the three variables a, b, and c with 5, 10, and "I am a" respectively so that they will not be undefined. // Initialize these three variables var a = 5; var b = 10; var c = "I am a"; // Do not change code below this line a = a + 1; b = b + 5; c = c + " String!";

When JavaScript variables are declared, they have an initial value of undefined. If you do a mathematical operation on an undefined variable your result will be NaN which means "Not a Number". If you concatenate a string with an undefined variable, you will get a literal string of "undefined".

Combine the if statements into a single if/else statement. function testElse(val) { var result = ""; // Only change code below this line if (val > 5) { result = "Bigger than 5"; } else { (val <= 5) result = "5 or Smaller"; } // Only change code above this line return result; } // Change this value to test testElse(4); You should only have one if statement in the editor Passed You should use an else statement Passed testElse(4) should return "5 or Smaller" Passed testElse(5) should return "5 or Smaller" Passed testElse(6) should return "Bigger than 5" Passed testElse(10) should return "Bigger than 5" Passed Do not change the code above or below the lines.

When a condition for an if statement is true, the block of code following it is executed. What about when that condition is false? Normally nothing would happen. With an else statement, an alternate block of code can be executed. if (num > 10) { return "Bigger than 10"; } else { return "10 or Less"; }

Modify the function abTest so that if a or b are less than 0 the function will immediately exit with a value of undefined. Hint Remember that undefined is a keyword, not a string. // Setup function abTest(a, b) { // Only change code below this line if ( b < 0 || a <0){ return undefined; } // Only change code above this line return Math.round(Math.pow(Math.sqrt(a) + Math.sqrt(b), 2)); } // Change values below to test your code abTest(-2,2); abTest(2,2) should return a number Passed abTest(2,2) should return 8 Passed abTest(-2,2) should return undefined Passed abTest(2,-2) should return undefined Passed abTest(2,8) should return 18 Passed abTest(3,3) should return 12

When a return statement is reached, the execution of the current function stops and control returns to the calling location. Example function myFun() { console.log("Hello"); return "World"; console.log("byebye") } myFun(); The above outputs "Hello" to the console, returns "World", but "byebye" is never output, because the function exits at the return statement.

Use backslashes to assign a string to the myStr variable so that if you were to print it to the console, you would see: I am a "double quoted" string inside "double quotes". var myStr = "I am a \"double quoted\" string inside \"double quotes\"."; // Change this line You should use two double quotes (") and four escaped double quotes (\"). Passed Variable myStr should contain the string: I am a "double quoted" string inside "double quotes".

When you are defining a string you must start and end with a single or double quote. What happens when you need a literal quote: " or ' inside of your string? In JavaScript, you can escape a quote from considering it as an end of string quote by placing a backslash (\) in front of the quote. var sampleStr = "Alan said, \"Peter is learning JavaScript\"."; This signals to JavaScript that the following quote is not the end of the string, but should instead appear inside the string. So if you were to print this to the console, you would get: Alan said, "Peter is learning JavaScript".

Modify the new array myArray so that it contains both a string and a number (in that order). Hint Refer to the example code in the text editor if you get stuck. // Example var ourArray = ["John", 23]; // Only change code below this line. var myArray = ["Eric", 23]; myArray should be an array. Passed The first item in myArray should be a string. Passed The second item in myArray should be a number.

With JavaScript array variables, we can store several pieces of data in one place. You start an array declaration with an opening square bracket, end it with a closing square bracket, and put a comma between each entry, like this: var sandwich = ["peanut butter", "jelly", "bread"].

Add a "bark" property to myDog and set it to a dog sound, such as "woof". You may use either dot or bracket notation. // Example var ourDog = { "name": "Camper", "legs": 4, "tails": 1, "friends": ["everything!"] }; ourDog.bark = "bow-wow"; // Setup var myDog = { "name": "Happy Coder", "legs": 4, "tails": 1, "friends": ["freeCodeCamp Campers"] }; // Only change code below this line. myDog["bark"] = "bark"; Add the property "bark" to myDog. Passed Do not add "bark" to the setup section

You can add new properties to existing JavaScript objects the same way you would modify them. Here's how we would add a "bark" property to ourDog: ourDog.bark = "bow-wow"; or ourDog["bark"] = "bow-wow"; Now when we evaluate ourDog.bark, we'll get his bark, "bow-wow".

Create a nested array called myArray. // Example var ourArray = [["the universe", 42], ["everything", 101010]]; // Only change code below this line. var myArray = [["the matrix", 2], ["reloaded", 110001]]; myArray should have at least one array nested within another array.

You can also nest arrays within other arrays, like this: [["Bulls", 23], ["White Sox", 45]]. This is also called a Multi-dimensional Array.

Let's try to set thirdLetterOfLastName to equal the third letter of the lastName variable using bracket notation. Hint Try looking at the secondLetterOfFirstName variable declaration if you get stuck. // Example var firstName = "Ada"; var secondLetterOfFirstName = firstName[1]; // Setup var lastName = "Lovelace"; // Only change code below this line. var thirdLetterOfLastName = lastName[2]; The thirdLetterOfLastName variable should have the value of v. Passed You should use bracket notation.

You can also use bracket notation to get the character at other positions within a string. Remember that computers start counting at 0, so the first character is actually the zeroth character.

Change the code to use the -- operator on myVar. var myVar = 11; // Only change code below this line myVar--;

You can easily decrement or decrease a variable by one with the -- operator. i--; is the equivalent of i = i - 1; Note The entire line becomes i--;, eliminating the need for the equal sign.

Change the code to use the ++ operator on myVar. var myVar = 87; // Only change code below this line myVar++;

You can easily increment or add one to a variable with the ++ operator. i++; is the equivalent of i = i + 1; Note The entire line becomes i++;, eliminating the need for the equal sign.

Use the .length property to count the number of characters in the lastName variable and assign it to lastNameLength. // Example var firstNameLength = 0; var firstName = "Ada"; firstNameLength = firstName.length; // Setup var lastNameLength = 0; var lastName = "Lovelace"; // Only change code below this line. lastNameLength = lastName; lastNameLength = lastName.length; lastNameLength should be equal to eight. Passed You should be getting the length of lastName by using .length like this: lastName.length.

You can find the length of a String value by writing .length after the string variable or string literal. "Alan Peter".length; // 10 For example, if we created a variable var firstName = "Charles", we could find out how long the string "Charles" is by using the firstName.length property.

Use bracket notation to find the second-to-last character in the lastName string. Hint Try looking at the thirdToLastLetterOfFirstName variable declaration if you get stuck. // Example var firstName = "Ada"; var thirdToLastLetterOfFirstName = firstName[firstName.length - 3]; // Setup var lastName = "Lovelace"; // Only change code below this line var secondToLastLetterOfLastName = lastName[lastName.length - 2]; secondToLastLetterOfLastName should be "c". Passed You have to use .length to get the second last letter.

You can use the same principle we just used to retrieve the last character in a string to retrieve the Nth-to-last character. For example, you can get the value of the third-to-last letter of the var firstName = "Charles" string by using firstName[firstName.length - 3]

Make an object that represents a dog called myDog which contains the properties "name" (a string), "legs", "tails" and "friends". You can set these object properties to whatever values you want, as long "name" is a string, "legs" and "tails" are numbers, and "friends" is an array. // Example var ourDog = { "name": "Camper", "legs": 4, "tails": 1, "friends": ["everything!"] }; // Only change code below this line. var myDog = { "name": "Fido", "legs": 4, "tails": 1, "friends": ["birb", "man"] }; myDog should contain the property name and it should be a string. Passed myDog should contain the property legs and it should be a number. Passed myDog should contain the property tails and it should be a number. Passed myDog should contain the property friends and it should be an array. Passed myDog should only contain all the given properties.

You may have heard the term object before. Objects are similar to arrays, except that instead of using indexes to access and modify their data, you access the data in objects through what are called properties. Objects are useful for storing data in a structured way, and can represent real world objects, like a cat. Here's a sample cat object: var cat = { "name": "Whiskers", "legs": 4, "tails": 1, "enemies": ["Water", "Dogs"] }; In this example, all the properties are stored as strings, such as - "name", "legs", and "tails". However, you can also use numbers as properties. You can even omit the quotes for single-word string properties, as follows: var anotherObject = { make: "Ford", 5: "five", "model": "focus" }; However, if your object has any non-string properties, JavaScript will automatically typecast them as strings.

Fix the function isLess to remove the if/else statements. function isLess(a, b) { // Fix this code return a < b; } // Change these values to test isLess(10, 15); isLess(10,15) should return true Passed isLess(15,10) should return false Passed You should not use any if or else statements

You may recall from Comparison with the Equality Operator that all comparison operators return a boolean true or false value. Sometimes people use an if/else statement to do a comparison, like this: function isEqual(a,b) { if (a === b) { return true; } else { return false; } } But there's a better way to do this. Since === returns true or false, we can return the result of the comparison: function isEqual(a,b) { return a === b; }

Write chained if/else if statements to fulfill the following conditions: num < 5 - return "Tiny" num < 10 - return "Small" num < 15 - return "Medium" num < 20 - return "Large" num >= 20 - return "Huge" function testSize(num) { // Only change code below this line if (num < 5) { return "Tiny"; } else if(num < 10) { return "Small"; } else if (num <15) { return "Medium"; } else if (num < 20) { return "Large"; } else { return "Huge" } return "Change Me"; // Only change code above this line } // Change this value to test testSize(7); You should have at least four else statements Passed You should have at least four if statements Passed You should have at least one return statement Passed testSize(0) should return "Tiny" Passed testSize(4) should return "Tiny" Passed testSize(5) should return "Small" Passed testSize(8) should return "Small" Passed testSize(10) should return "Medium" Passed testSize(14) should return "Medium" Passed testSize(15) should return "Large" Passed testSize(17) should return "Large" Passed testSize(20) should return "Huge" Passed testSize(25) should return "Huge"

if/else statements can be chained together for complex logic. Here is pseudocode of multiple chained if / else if statements: if (condition1) { statement1 } else if (condition2) { statement2 } else if (condition3) { statement3 . . . } else { statementN }

Assign the value 7 to variable a. Assign the contents of a to variable b. // Setup var a; var b = 2; // Only change code below this line var a = 7; var b = a;

myVariable = 5; This assigns the Number value 5 to myVariable. Assignment always goes from right to left. Everything to the right of the = operator is resolved before the value is assigned to the variable to the left of the operator. myVar = 5; myNum = myVar; This assigns 5 to myVar and then resolves myVar to 5 again and assigns it to myNum

// Example var ourName; var myName; // Declare myName below this line

n computer science, data is anything that is meaningful to the computer. JavaScript provides seven different data types which are undefined, null, boolean, string, symbol, number, and object. For example, computers distinguish between numbers, such as the number 12, and strings, such as "12", "dog", or "123 cats", which are collections of characters. Computers can perform mathematical operations on a number, but not on a string. Variables allow computers to store and manipulate data in a dynamic fashion. They do this by using a "label" to point to the data rather than using the data itself. Any of the seven data types may be stored in a variable. Variables are similar to the x and y variables you use in mathematics, which means they're a simple name to represent the data we want to refer to. Computer variables differ from mathematical variables in that they can store different values at different times.

Use the .shift() function to remove the first item from myArray, assigning the "shifted off" value to removedFromMyArray. // Example var ourArray = ["Stimpson", "J", ["cat"]]; var removedFromOurArray = ourArray.shift(); // removedFromOurArray now equals "Stimpson" and ourArray now equals ["J", ["cat"]]. // Setup var myArray = [["John", 23], ["dog", 3]]; // Only change code below this line. var removedFromMyArray = myArray.shift(); myArray should now equal [["dog", 3]]. Passed removedFromMyArray should contain ["John", 23]

pop() always removes the last element of an array. What if you want to remove the first? That's where .shift() comes in. It works just like .pop(), except it removes the first element instead of the last.

Create a function addFive without any arguments. This function adds 5 to the sum variable, but its returned value is undefined. // Example var sum = 0; function addThree() { sum = sum + 3; } // Only change code below this line function addFive(num) { sum = sum + 5; } var returnedValue = addFive(5); // Only change code above this line var returnedValue = addFive(); addFive should be a function Passed sum should be equal to 8 Passed Returned value from addFive should be undefined Passed Inside of your functions, add 5 to the sum variable

A function can include the return statement but it does not have to. In the case that the function doesn't have a return statement, when you call it, the function processes the inner code but the returned value is undefined. Example var sum = 0; function addSum(num) { sum = sum + num; } var returnedValue = addSum(3); // sum will be modified but returned value is undefined addSum is a function without a return statement. The function will change the global sum variable but the returned value of the function is undefined

Change the 0 so that the quotient is equal to 2. var quotient = 66 / 33;

We can also divide one number by another. JavaScript uses the / symbol for division. Example myVar = 16 / 2; // assigned 8

Change the 0 so that product will equal 80. var product = 8 * 10;

We can also multiply one number by another. JavaScript uses the * symbol for multiplication of two numbers. Example myVar = 13 * 13; // assigned 169

Change the 0 so the difference is 12. var difference = 45 - 33;

We can also subtract one number from another. JavaScript uses the - symbol for subtraction.

Push ["dog", 3] onto the end of the myArray variable. // Example var ourArray = ["Stimpson", "J", "cat"]; ourArray.push(["happy", "joy"]); // ourArray now equals ["Stimpson", "J", "cat", ["happy", "joy"]] // Setup var myArray = [["John", 23], ["cat", 2]]; // Only change code below this line. myArray.push(["dog", 3])

An easy way to append data to the end of an array is via the push() function. .push() takes one or more parameters and "pushes" them onto the end of the array. var arr = [1,2,3]; arr.push(4); // arr is now [1,2,3,4]

Modify the welcomeToBooleans function so that it returns true instead of false when the run button is clicked. function welcomeToBooleans() { // Only change code below this line. return true; // Change this line // Only change code above this line. } The welcomeToBooleans() function should return a boolean (true/false) value. Passed welcomeToBooleans() should return true.

Another data type is the Boolean. Booleans may only be one of two values: true or false. They are basically little on-off switches, where true is "on" and false is "off." These two states are mutually exclusive. Note Boolean values are never written with quotes. The strings "true" and "false" are not Boolean and have no special meaning in JavaScript.

Use the playerNumber variable to look up player 16 in testObj using bracket notation. Then assign that name to the player variable. // Setup var testObj = { 12: "Namath", 16: "Montana", 19: "Unitas" }; // Only change code below this line; var playerNumber = 16; // Change this Line var player = testObj[playerNumber]; // Change this Line playerNumber should be a number Passed The variable player should be a string Passed The value of player should be "Montana" Passed You should use bracket notation to access testObj Passed You should not assign the value Montana to the variable player directly. Passed You should be using the variable playerNumber in your bracket notation

Another use of bracket notation on objects is to access a property which is stored as the value of a variable. This can be very useful for iterating through an object's properties or when accessing a lookup table. Here is an example of using a variable to access a property: var dogs = { Fido: "Mutt", Hunter: "Doberman", Snoopie: "Beagle" }; var myDog = "Hunter"; var myBreed = dogs[myDog]; console.log(myBreed); // "Doberman" Another way you can use this concept is when the property's name is collected dynamically during the program execution, as follows: var someObj = { propName: "John" }; function propPrefix(str) { var s = "prop"; return s + str; } var someProp = propPrefix("Name"); // someProp now holds the value 'propName' console.log(someObj[someProp]); // "John" Note that we do not use quotes around the variable name when using it to access the property because we are using the value of the variable, not the name.

Use the .pop() function to remove the last item from myArray, assigning the "popped off" value to removedFromMyArray. // Example var ourArray = [1,2,3]; var removedFromOurArray = ourArray.pop(); // removedFromOurArray now equals 3, and ourArray now equals [1,2] // Setup var myArray = [["John", 23], ["cat", 2]]; // Only change code below this line. var removedFromMyArray = myArray.pop(); myArray should only contain [["John", 23]]. Passed Use pop() on myArray Passed removedFromMyArray should only contain ["cat", 2]

Another way to change the data in an array is with the .pop() function. .pop() is used to "pop" a value off of the end of an array. We can store this "popped off" value by assigning it to a variable. In other words, .pop() removes the last element from an array and returns that element. Any type of entry can be "popped" off of an array - numbers, strings, even nested arrays. var threeArr = [1, 4, 6]; var oneDown = threeArr.pop(); console.log(oneDown); // Returns 6 console.log(threeArr); // Returns [1, 4]

Create an if statement inside the function to return "Yes, that was true" if the parameter wasThatTrue is true and return "No, that was false" otherwise. // Example function ourTrueOrFalse(isItTrue) { if (isItTrue) { return "Yes, it's true"; } return "No, it's false"; } // Setup function trueOrFalse(wasThatTrue) { // Only change code below this line. if (wasThatTrue) { return "Yes, that was true" } return"No, that was false" // Only change code above this line. } // Change this value to test trueOrFalse(true); trueOrFalse should be a function Passed trueOrFalse(true) should return a string Passed trueOrFalse(false) should return a string Passed trueOrFalse(true) should return "Yes, that was true" Passed trueOrFalse(false) should return "No, that was false"

If statements are used to make decisions in code. The keyword if tells JavaScript to execute the code in the curly braces under certain conditions, defined in the parentheses. These conditions are known as Boolean conditions and they may only be true or false. When the condition evaluates to true, the program executes the statement inside the curly braces. When the Boolean condition evaluates to false, the statement inside the curly braces will not execute. Pseudocode if (condition is true) { statement is executed } Example function test (myCondition) { if (myCondition) { return "It was true"; } return "It was false"; } test(true); // returns "It was true" test(false); // returns "It was false" When test is called with a value of true, the if statement evaluates myCondition to see if it is true or not. Since it is true, the function returns "It was true". When we call test with a value of false, myCondition is not true and the statement in the curly braces is not executed and the function returns "It was false".

Write a switch statement to set answer for the following ranges: 1-3 - "Low" 4-6 - "Mid" 7-9 - "High" Note You will need to have a case statement for each number in the range. function sequentialSizes(val) { var answer = ""; // Only change code below this line switch(val) { case 1: case 2: case 3: answer = "Low"; break; case 4: case 5: case 6: answer = "Mid"; break; case 7: case 8: case 9: answer= "High"; break; } // Only change code above this line return answer; } // Change this value to test sequentialSizes(1);

If the break statement is omitted from a switch statement's case, the following case statement(s) are executed until a break is encountered. If you have multiple inputs with the same output, you can represent them in a switch statement like this: switch(val) { case 1: case 2: case 3: result = "1, 2, or 3"; break; case 4: result = "4 alone"; } Cases for 1, 2, and 3 will all produce the same result. sequentialSizes(1) should return "Low" Passed sequentialSizes(2) should return "Low" Passed sequentialSizes(3) should return "Low" Passed sequentialSizes(4) should return "Mid" Passed sequentialSizes(5) should return "Mid" Passed sequentialSizes(6) should return "Mid" Passed sequentialSizes(7) should return "High" Passed sequentialSizes(8) should return "High" Passed sequentialSizes(9) should return "High" Passed You should not use any if or else statements Passed You should have nine case statements

if (val === "bob") { answer = "Marley"; } else if (val === 42) { answer = "The Answer"; } else if (val === 1) { answer = "There is no #1"; } else if (val === 99) { answer = "Missed me by this much!"; } else if (val === 7) { answer = "Ate Nine"; } Change the chained if/else if statements into a switch statement. function chainToSwitch(val) { var answer = ""; // Only change code below this line switch(val) { case "bob": answer="Marley"; break; case 42: answer="The Answer"; break; case 1: answer = "There is no #1"; break; case 99: answer = "Missed me by this much!"; break; case 7: answer = "Ate Nine"; } // Only change code above this line return answer; } // Change this value to test chainToSwitch(7);

If you have many options to choose from, a switch statement can be easier to write than many chained if/else if statements. The following: if (val === 1) { answer = "a"; } else if (val === 2) { answer = "b"; } else { answer = "c"; } can be replaced with: switch(val) { case 1: answer = "a"; break; case 2: answer = "b"; break; default: answer = "c"; } You should not use any else statements anywhere in the editor Passed You should not use any if statements anywhere in the editor Passed You should have at least four break statements Passed chainToSwitch("bob") should be "Marley" Passed chainToSwitch(42) should be "The Answer" Passed chainToSwitch(1) should be "There is no #1" Passed chainToSwitch(99) should be "Missed me by this much!" Passed chainToSwitch(7) should be "Ate Nine" Passed chainToSwitch("John") should be "" (empty string) Passed chainToSwitch(156) should be "" (empty string)

Create a function called reusableFunction which prints "Hi World" to the dev console. Call the function. function reusableFunction() { console.log("Hi World"); } reusableFunction(); reusableFunction should be a function Passed reusableFunction should output "Hi World" to the dev console Passed Call reusableFunction after you define it

In JavaScript, we can divide up our code into reusable parts called functions. Here's an example of a function: function functionName() { console.log("Hello World"); } You can call or invoke this function by using its name followed by parentheses, like this: functionName(); Each time the function is called it will print out the message "Hello World" on the dev console. All of the code between the curly braces will be executed every time the function is called.

Write a switch statement which tests val and sets answer for the following conditions: 1 - "alpha" 2 - "beta" 3 - "gamma" 4 - "delta" function caseInSwitch(val) { var answer = ""; // Only change code below this line switch(val) { case 1: answer="alpha"; break; case 2: answer="beta"; break; case 3: answer="gamma"; break; case 4: answer="delta"; break; } // Only change code above this line return answer; } // Change this value to test caseInSwitch(1); caseInSwitch(1) should have a value of "alpha" Passed caseInSwitch(2) should have a value of "beta" Passed caseInSwitch(3) should have a value of "gamma" Passed caseInSwitch(4) should have a value of "delta" Passed You should not use any if or else statements Passed You should have at least 3 break statements

If you have many options to choose from, use a switch statement. A switch statement tests a value and can have many case statements which define various possible values. Statements are executed from the first matched case value until a break is encountered. Here is a pseudocode example: switch(num) { case value1: statement1; break; case value2: statement2; break; ... case valueN: statementN; break; } case values are tested with strict equality (===). The break tells JavaScript to stop executing statements. If the break is omitted, the next statement will be executed.

Convert the logic to use else if statements. function testElseIf(val) { if (val > 10) { return "Greater than 10"; } else if (val < 5) { return "Smaller than 5"; } else { return "Between 5 and 10"; } } // Change this value to test testElseIf(7); You should have at least two else statements Passed You should have at least two if statements Passed You should have closing and opening curly braces for each condition Passed testElseIf(0) should return "Smaller than 5" Passed testElseIf(5) should return "Between 5 and 10" Passed testElseIf(7) should return "Between 5 and 10" Passed testElseIf(10) should return "Between 5 and 10" Passed testElseIf(12) should return "Greater than 10"

If you have multiple conditions that need to be addressed, you can chain if statements together with else if statements. if (num > 15) { return "Bigger than 15"; } else if (num < 5) { return "Smaller than 5"; } else { return "Between 5 and 15"; }

Call the processArg function with an argument of 7 and assign its return value to the variable processed. // Example var changed = 0; function change(num) { return (num + 5) / 3; } changed = change(10); // Setup var processed = 0; function processArg(num) { return (num + 3) / 5; } // Only change code below this line processed = processArg(7); processed should have a value of 2 Passed You should assign processArg to processed

If you'll recall from our discussion of Storing Values with the Assignment Operator, everything to the right of the equal sign is resolved before the value is assigned. This means we can take the return value of a function and assign it to a variable. Assume we have pre-defined a function sum which adds two numbers together, then: ourSum = sum(5, 12); will call sum function, which returns a value of 17 and assigns it to ourSum variable.

function nextInLine(arr, item) { // Your code here arr.push(item); var removed = arr.shift(); return removed; // Change this line } // Test Setup var testArr = [1,2,3,4,5]; // Display Code console.log("Before: " + JSON.stringify(testArr)); console.log(nextInLine(testArr, 6)); // Modify this line to test console.log("After: " + JSON.stringify(testArr)); nextInLine([], 5) should return a number. Passed nextInLine([], 1) should return 1 Passed nextInLine([2], 1) should return 2 Passed nextInLine([5,6,7,8,9], 1) should return 5 Passed After nextInLine(testArr, 10), testArr[4] should be 10

In Computer Science a queue is an abstract Data Structure where items are kept in order. New items can be added at the back of the queue and old items are taken off from the front of the queue. Write a function nextInLine which takes an array (arr) and a number (item) as arguments. Add the number to the end of the array, then remove the first element of the array. The nextInLine function should then return the element that was removed.

Modify the existing declarations and assignments so their names use camelCase. Do not create any new variables. // Declarations var studlyCapVar = 10; var properCamelCase = "A String"; var titleCaseOver = 9000; // Assignments studlyCapVar = 10; properCamelCase = "A String"; titleCaseOver = 9000;

In JavaScript all variables and function names are case sensitive. This means that capitalization matters. MYVAR is not the same as MyVar nor myvar. It is possible to have multiple distinct variables with the same name but different casing. It is strongly recommended that for the sake of clarity, you do not use this language feature. Best Practice Write variable names in JavaScript in camelCase. In camelCase, multi-word variable names have the first word in lowercase and the first letter of each subsequent word is capitalized. var someVariable; var anotherVariableName; var thisVariableNameIsSoLong;

Correct the assignment to myStr so it contains the string value of Hello World using the approach shown in the example above. // Setup var myStr = "Jello World"; // Only change code below this line myStr = "Hello World"; // Fix Me myStr should have a value of Hello World Passed Do not change the code above the line

In JavaScript, String values are immutable, which means that they cannot be altered once created. For example, the following code: var myStr = "Bob"; myStr[0] = "J"; cannot change the value of myStr to "Job", because the contents of myStr cannot be altered. Note that this does not mean that myStr cannot be changed, just that the individual characters of a string literal cannot be changed. The only way to change myStr would be to assign it with a new string, like this: var myStr = "Bob"; myStr = "Job";

Using var, declare a global variable myGlobal outside of any function. Initialize it with a value of 10. Inside function fun1, assign 5 to oopsGlobal without using the var keyword. // Declare your variable here oopsGlobal = 5; var myGlobal = 10; function fun1() { // Assign 5 to oopsGlobal Here var output= ""; if (typeof myGlobal != "undefined") { output += "myGlobal: " + myGlobal; } if (typeof oopsGlobal != 'undefined') { output += " oopsGlobal: " + oopsGlobal; } console.log(output); } // Only change code above this line function fun2() { var output = ""; if (typeof myGlobal != "undefined") { output += "myGlobal: " + myGlobal; } if (typeof oopsGlobal != "undefined") { output += " oopsGlobal: " + oopsGlobal; } console.log(output); } myGlobal should be defined Passed myGlobal should have a value of 10 Passed myGlobal should be declared using the var keyword Passed oopsGlobal should be a global variable and have a value of 5

In JavaScript, scope refers to the visibility of variables. Variables which are defined outside of a function block have Global scope. This means, they can be seen everywhere in your JavaScript code. Variables which are used without the var keyword are automatically created in the global scope. This can create unintended consequences elsewhere in your code or when running a function again. You should always declare your variables with var.

Write a switch statement to set answer for the following conditions: "a" - "apple" "b" - "bird" "c" - "cat" default - "stuff" function switchOfStuff(val) { var answer = ""; // Only change code below this line switch(val) { case "a": answer = "apple"; break; case "b": answer = "bird"; break; case "c": answer = "cat"; break; default: answer = "stuff"; break; } // Only change code above this line return answer; } // Change this value to test switchOfStuff(1); switchOfStuff("a") should have a value of "apple" Passed switchOfStuff("b") should have a value of "bird" Passed switchOfStuff("c") should have a value of "cat" Passed switchOfStuff("d") should have a value of "stuff" Passed switchOfStuff(4) should have a value of "stuff" Passed You should not use any if or else statements Passed You should use a default statement Passed You should have at least 3 break statements

In a switch statement you may not be able to specify all possible values as case statements. Instead, you can add the default statement which will be executed if no matching case statements are found. Think of it like the final else statement in an if/else chain. A default statement should be the last case. switch (num) { case value1: statement1; break; case value2: statement2; break; ... default: defaultStatement; break; }

Use bracket notation to find the last character in the lastName variable. Hint Try looking at the lastLetterOfFirstName variable declaration if you get stuck.

In order to get the last letter of a string, you can subtract one from the string's length. For example, if var firstName = "Charles", you can get the value of the last letter of the string by using firstName[firstName.length - 1].

Use bracket notation to find the last character in the lastName variable. Hint Try looking at the lastLetterOfFirstName variable declaration if you get stuck. // Example var firstName = "Ada"; var lastLetterOfFirstName = firstName[firstName.length - 1]; // Setup var lastName = "Lovelace"; // Only change code below this line. var lastLetterOfLastName = lastName[lastName.length - 1]; lastLetterOfLastName should be "e". Passed You have to use .length to get the last letter.

Convert the assignments for a, b, and c to use the += operator.

In programming, it is common to use assignments to modify the contents of a variable. Remember that everything to the right of the equals sign is evaluated first, so we can say: myVar = myVar + 5; to add 5 to myVar. Since this is such a common pattern, there are operators which do both a mathematical operation and assignment in one step. One such operator is the += operator. var myVar = 1; myVar += 5; console.log(myVar); // Returns 6

Convert the assignments for a, b, and c to use the += operator. var a = 3; var b = 17; var c = 12; // Only modify code below this line a = a += 12; b = b +=9; c = c +=7; a should equal 15 Passed b should equal 26 Passed c should equal 19 Passed You should use the += operator for each variable Passed Do not modify the code above the line

In the casino game Blackjack, a player can gain an advantage over the house by keeping track of the relative number of high and low cards remaining in the deck. This is called Card Counting. Having more high cards remaining in the deck favors the player. Each card is assigned a value according to the table below. When the count is positive, the player should bet high. When the count is zero or negative, the player should bet low. Count Change Cards +1 2, 3, 4, 5, 6 0 7, 8, 9 -1 10, 'J', 'Q', 'K', 'A' You will write a card counting function. It will receive a card parameter, which can be a number or a string, and increment or decrement the global count variable according to the card's value (see table). The function will then return a string with the current count and the string Bet if the count is positive, or Hold if the count is zero or negative. The current count and the player's decision (Bet or Hold) should be separated by a single space. Example Output -3 Hold 5 Bet Hint Do NOT reset count to 0 when value is 7, 8, or 9. Do NOT return an array. Do NOT include quotes (single or double) in the output.

Strokes Return 1 "Hole-in-one!" <= par - 2 "Eagle" par - 1 "Birdie" par "Par" par + 1 "Bogey" par + 2 "Double Bogey" >= par + 3 "Go Home!" par and strokes will always be numeric and positive. We have added an array of all the names for your convenience. var names = ["Hole-in-one!", "Eagle", "Birdie", "Par", "Bogey", "Double Bogey", "Go Home!"]; function golfScore(par, strokes) { // Only change code below this line if (strokes ==1){ return "Hole-in-one!" } else if (strokes <=par-2){ return "Eagle"; } else if (strokes == par-1){ return "Birdie"; } else if (strokes == par){ return "Par"; } else if (strokes == par+1){ return "Bogey"; } else if (strokes == par+2) { return "Double Bogey"; } else { return "Go Home!" } return "Change Me"; // Only change code above this line } // Change these values to test golfScore(5, 4);

In the game of golf each hole has a par meaning the average number of strokes a golfer is expected to make in order to sink the ball in a hole to complete the play. Depending on how far above or below par your strokes are, there is a different nickname. Your function will be passed par and strokes arguments. Return the correct string according to this table which lists the strokes in order of priority; top (highest) to bottom (lowest): golfScore(4, 1) should return "Hole-in-one!" Passed golfScore(4, 2) should return "Eagle" Passed golfScore(5, 2) should return "Eagle" Passed golfScore(4, 3) should return "Birdie" Passed golfScore(4, 4) should return "Par" Passed golfScore(1, 1) should return "Hole-in-one!" Passed golfScore(5, 5) should return "Par" Passed golfScore(4, 5) should return "Bogey" Passed golfScore(4, 6) should return "Double Bogey" Passed golfScore(4, 7) should return "Go Home!" Passed golfScore(5, 9) should return "Go Home!"

The compareEquality function in the editor compares two values using the equality operator. Modify the function so that it returns "Equal" only when the values are strictly equal. // Setup function compareEquality(a, b) { if (a === b) { // Change this line return "Equal"; } return "Not Equal"; } // Change this value to test compareEquality(10, "10"); compareEquality(10, "10") should return "Not Equal" Passed compareEquality("20", 20) should return "Not Equal" Passed You should use the === operator

In the last two challenges, we learned about the equality operator (==) and the strict equality operator (===). Let's do a quick review and practice using these operators some more. If the values being compared are not of the same type, the equality operator will perform a type conversion, and then evaluate the values. However, the strict equality operator will compare both the data type and value as-is, without converting one type to the other. Examples 3 == '3' // returns true because JavaScript performs type conversion from string to number 3 === '3' // returns false because the types are different and type conversion is not performed Note In JavaScript, you can determine the type of a variable or a value with the typeof operator, as follows: typeof 3 // returns 'number' typeof '3' // returns 'string'

Define a variable a with var and initialize it to a value of 9. // Example var ourVar = 19; // Only change code below this line var a = 9;

It is common to initialize a variable to an initial value in the same line as it is declared. var myVar = 0; Creates a new variable called myVar and assigns it an initial value of 0

Add a local variable to myOutfit function to override the value of outerWear with "sweater". // Setup var outerWear = "T-Shirt"; function myOutfit() { // Only change code below this line var outerWear = "sweater"; // Only change code above this line return outerWear; } myOutfit(); Do not change the value of the global outerWear Passed myOutfit should return "sweater" Passed Do not change the return statement

It is possible to have both local and global variables with the same name. When you do this, the local variable takes precedence over the global variable. In this example: var someVar = "Hat"; function myFun() { var someVar = "Head"; return someVar; } The function myFun will return "Head" because the local version of the variable is present.

Set someAdjective and append it to myStr using the += operator. // Example var anAdjective = "awesome!"; var ourStr = "freeCodeCamp is "; ourStr += anAdjective; // Only change code below this line var someAdjective = "fun"; var myStr = "Learning to code is "; myStr += someAdjective; someAdjective should be set to a string at least 3 characters long Passed Append someAdjective to myStr using the += operator

Just as we can build a string over multiple lines out of string literals, we can also append variables to a string using the plus equals (+=) operator.

Convert the assignments for a, b, and c to use the -= operator. var a = 11; var b = 9; var c = 3; // Only modify code below this line a -= 6; b -= 15; c -= 1; a should equal 5 Passed b should equal -6 Passed c should equal 2 Passed You should use the -= operator for each variable Passed Do not modify the code above the line

Like the += operator, -= subtracts a number from a variable. myVar = myVar - 5; will subtract 5 from myVar. This can be rewritten as: myVar -= 5;

Add ["Paul",35] to the beginning of the myArray variable using unshift(). // Example var ourArray = ["Stimpson", "J", "cat"]; ourArray.shift(); // ourArray now equals ["J", "cat"] ourArray.unshift("Happy"); // ourArray now equals ["Happy", "J", "cat"] // Setup var myArray = [["John", 23], ["dog", 3]]; myArray.shift(); // Only change code below this line. myArray.unshift(["Paul", 35]) myArray should now have [["Paul", 35], ["dog", 3]].

Not only can you shift elements off of the beginning of an array, you can also unshift elements to the beginning of an array i.e. add elements in front of the array. .unshift() works exactly like .push(), but instead of adding the element at the end of the array, unshift() adds the element at the beginning of the array.

Change the 0.0 so that quotient will equal to 2.2. var quotient = 4.4 / 2.0; // Fix this line

Now let's divide one decimal by another.

Change the 0 so that sum will equal 20. var sum = 10 + 10;

Number is a data type in JavaScript which represents numeric data. Now let's try to add two numbers using JavaScript. JavaScript uses the + symbol as addition operation when placed between two numbers.

Create two new string variables: myFirstName and myLastName and assign them the values of your first and last name, respectively. // Example var firstName = "Alan"; var lastName = "Turing"; // Only change code below this line var myFirstName = "Eric"; var myLastName = "Harrison"

Previously we have used the code var myName = "your name"; "your name" is called a string literal. It is a string because it is a series of zero or more characters enclosed in single or double quotes.

Convert the switch statement into an object called lookup. Use it to look up val and assign the associated string to the result variable. // Setup function phoneticLookup(val) { var result = ""; // Only change code below this line var lookup = { "alpha": "Adams", "bravo": "Boston", "charlie": "Chicago", "delta": "Denver", "echo": "Easy", "foxtrot": "Frank" }; result = lookup[val]; // Only change code above this line return result; } // Change this value to test phoneticLookup("charlie"); phoneticLookup("alpha") should equal "Adams" Passed phoneticLookup("bravo") should equal "Boston" Passed phoneticLookup("charlie") should equal "Chicago" Passed phoneticLookup("delta") should equal "Denver" Passed phoneticLookup("echo") should equal "Easy" Passed phoneticLookup("foxtrot") should equal "Frank" Passed phoneticLookup("") should equal undefined Passed You should not modify the return statement Passed You should not use case, switch, or if statements

Objects can be thought of as a key/value storage, like a dictionary. If you have tabular data, you can use an object to "lookup" values rather than a switch statement or an if/else chain. This is most useful when you know that your input data is limited to a certain range. Here is an example of a simple reverse alphabet lookup: var alpha = { 1:"Z", 2:"Y", 3:"X", 4:"W", ... 24:"C", 25:"B", 26:"A" }; alpha[2]; // "Y" alpha[24]; // "C" var value = 2; alpha[value]; // "Y" Original Code For Problem: // Setup function phoneticLookup(val) { var result = ""; // Only change code below this line switch(val) { case "alpha": result = "Adams"; break; case "bravo": result = "Boston"; break; case "charlie": result = "Chicago"; break; case "delta": result = "Denver"; break; case "echo": result = "Easy"; break; case "foxtrot": result = "Frank"; } // Only change code above this line return result; } // Change this value to test phoneticLookup("charlie");

Using bracket notation select an element from myArray such that myData is equal to 8. // Setup var myArray = [[1,2,3], [4,5,6], [7,8,9], [[10,11,12], 13, 14]]; // Only change code below this line. var myData = myArray[2][1]; myData should be equal to 8. Passed You should be using bracket notation to read the correct value from myArray.

One way to think of a multi-dimensional array, is as an array of arrays. When you use brackets to access your array, the first set of brackets refers to the entries in the outer-most (the first level) array, and each additional pair of brackets refers to the next level of entries inside. Example var arr = [ [1,2,3], [4,5,6], [7,8,9], [[10,11,12], 13, 14] ]; arr[3]; // equals [[10,11,12], 13, 14] arr[3][0]; // equals [10,11,12] arr[3][0][1]; // equals 11 Note There shouldn't be any spaces between the array name and the square brackets, like array [0][0] and even this array [0] [0] is not allowed. Although JavaScript is able to process this correctly, this may confuse other programmers reading your code.

Change the order of logic in the function so that it will return the correct statements in all cases. function orderMyLogic(val) { if (val < 5) { return "Less than 5"; } else if (val < 10) { return "Less than 10"; } else { return "Greater than or equal to 10"; } } // Change this value to test orderMyLogic(7); orderMyLogic(4) should return "Less than 5" Passed orderMyLogic(6) should return "Less than 10" Passed orderMyLogic(11) should return "Greater than or equal to 10"

Order is important in if, else if statements. The function is executed from top to bottom so you will want to be careful of what statement comes first. Take these two functions as an example. Here's the first: function foo(x) { if (x < 1) { return "Less than one"; } else if (x < 2) { return "Less than two"; } else { return "Greater than or equal to two"; } } And the second just switches the order of the statements: function bar(x) { if (x < 2) { return "Less than two"; } else if (x < 1) { return "Less than one"; } else { return "Greater than or equal to two"; } } While these two functions look nearly identical if we pass a number to both we get different outputs. foo(0) // "Less than one" bar(0) // "Less than two"

Create a function called functionWithArgs that accepts two arguments and outputs their sum to the dev console. Call the function with two numbers as arguments. // Example function ourFunctionWithArgs(a, b) { console.log(a - b); } ourFunctionWithArgs(10, 5); // Outputs 5 // Only change code below this line. function functionWithArgs(a,b) { console.log(a+b); } functionWithArgs(1+3); functionWithArgs(7,9); functionWithArgs should be a function Passed functionWithArgs(1,2) should output 3 Passed functionWithArgs(7,9) should output 16 Passed Call functionWithArgs with two numbers after you define it.

Parameters are variables that act as placeholders for the values that are to be input to a function when it is called. When a function is defined, it is typically defined along with one or more parameters. The actual values that are input (or "passed") into a function when it is called are known as arguments. Here is a function with two parameters, param1 and param2: function testFun(param1, param2) { console.log(param1, param2); } Then we can call testFun: testFun("Hello", "World"); We have passed two arguments, "Hello" and "World". Inside the function, param1 will equal "Hello" and param2 will equal "World". Note that you could call testFun again with different arguments and the parameters would take on the value of the new arguments.

Assign the following three lines of text into the single variable myStr using escape sequences. FirstLine \SecondLine ThirdLine You will need to use escape sequences to insert special characters correctly. You will also need to follow the spacing as it looks above, with no spaces between escape sequences or words. Here is the text with the escape sequences written out. "FirstLine" "newline" "tab" "backslash" "SecondLine" "newline" "ThirdLine" var myStr = "FirstLine\n\tab\\SecondLine\nThirdLine"; // Change this line myStr should not contain any spaces Passed myStr should contain the strings FirstLine, SecondLine and ThirdLine (remember case sensitivity) Passed FirstLine should be followed by the newline character \n Passed myStr should contain a tab character \t which follows a newline character Passed SecondLine should be preceded by the backslash character \\ Passed There should be a newline character between SecondLine and ThirdLine

Quotes are not the only characters that can be escaped inside a string. There are two reasons to use escaping characters: First is to allow you to use characters you might not otherwise be able to type out, such as a backspace. Second is to allow you to represent multiple quotes in a string without JavaScript misinterpreting what you mean. We learned this in the previous challenge. Code Output \' single quote \" double quote \\ backslash \n newline \r carriage return \t tab \b backspace \f form feed Note that the backslash itself must be escaped in order to display as a backslash.

Modify the function checkObj to test myObj for checkProp. If the property is found, return that property's value. If not, return "Not Found". // Setup var myObj = { gift: "pony", pet: "kitten", bed: "sleigh" }; function checkObj(checkProp) { // Your Code Here if (myObj.hasOwnProperty(checkProp)) return myObj[checkProp]; return "Not Found"; } // Test your code by modifying these values checkObj("gift"); checkObj("gift") should return "pony". Passed checkObj("pet") should return "kitten". Passed checkObj("house") should return "Not Found".

Sometimes it is useful to check if the property of a given object exists or not. We can use the .hasOwnProperty(propname) method of objects to determine if that object has the given property name. .hasOwnProperty() returns true or false if the property is found or not. Example var myObj = { top: "hat", bottom: "pants" }; myObj.hasOwnProperty("top"); // true myObj.hasOwnProperty("middle"); // false

Set myName to a string equal to your name and build myStr with myName between the strings "My name is " and " and I am well!" // Example var ourName = "freeCodeCamp"; var ourStr = "Hello, our name is " + ourName + ", how are you?"; // Only change code below this line var myName = "Eric"; var myStr = "My name is " + myName + " and I am well!"; myName should be set to a string at least 3 characters long Passed Use two + operators to build myStr with myName inside it

Sometimes you will need to build a string, Mad Libs style. By using the concatenation operator (+), you can insert one or more variables into a string you're building

Combine the two if statements into one statement which will return "Yes" if val is less than or equal to 50 and greater than or equal to 25. Otherwise, will return "No". function testLogicalAnd(val) { // Only change code below this line if (val <= 50 && val >=25) { return "Yes"; } // Only change code above this line return "No"; } // Change this value to test testLogicalAnd(10); You should use the && operator once Passed You should only have one if statement Passed testLogicalAnd(0) should return "No" Passed testLogicalAnd(24) should return "No" Passed testLogicalAnd(25) should return "Yes" Passed testLogicalAnd(30) should return "Yes" Passed testLogicalAnd(50) should return "Yes" Passed testLogicalAnd(51) should return "No" Passed testLogicalAnd(75) should return "No" Passed testLogicalAnd(80) should return "No"

Sometimes you will need to test more than one thing at a time. The logical and operator (&&) returns true if and only if the operands to the left and right of it are true. The same effect could be achieved by nesting an if statement inside another if: if (num > 5) { if (num < 10) { return "Yes"; } } return "No"; will only return "Yes" if num is greater than 5 and less than 10. The same logic can be written as: if (num > 5 && num < 10) { return "Yes"; } return "No";

Use the strict equality operator in the if statement so the function will return "Equal" when val is strictly equal to 7 // Setup function testStrict(val) { if (val === 7) { // Change this line return "Equal"; } return "Not Equal"; } // Change this value to test testStrict(10); Use the strict equality operator in the if statement so the function will return "Equal" when val is strictly equal to 7 testStrict(10) should return "Not Equal" Passed testStrict(7) should return "Equal" Passed testStrict("7") should return "Not Equal" Passed You should use the === operator

Strict equality (===) is the counterpart to the equality operator (==). However, unlike the equality operator, which attempts to convert both values being compared to a common type, the strict equality operator does not perform a type conversion. If the values being compared have different types, they are considered unequal, and the strict equality operator will return false. Examples 3 === 3 // true 3 === '3' // false In the second example, 3 is a Number type and '3' is a String type.

Change the provided string to a string with single quotes at the beginning and end and no escape characters. Right now, the <a> tag in the string uses double quotes everywhere. You will need to change the outer quotes to single quotes so you can remove the escape characters. var myStr = '<a href="http://www.example.com" target="_blank">Link</a>'; Remove all the backslashes (\) Passed You should have two single quotes ' and four double quotes "

String values in JavaScript may be written with single or double quotes, as long as you start and end with the same type of quote. Unlike some other programming languages, single and double quotes work the same in JavaScript. doubleQuoteStr = "This is a string"; singleQuoteStr = 'This is also a string'; The reason why you might want to use one type of quote over the other is if you want to use both in a string. This might happen if you want to save a conversation in a string and have the conversation in quotes. Another use for it would be saving an <a> tag with various attributes in quotes, all within a string. conversation = 'Finn exclaims to Jake, "Algebraic!"'; However, this becomes a problem if you need to use the outermost quotes within it. Remember, a string has the same kind of quote at the beginning and end. But if you have that same quote somewhere in the middle, the string will stop early and throw an error. goodStr = 'Jake asks Finn, "Hey, let\'s go on an adventure?"'; badStr = 'Finn responds, "Let's go!"'; // Throws an error In the goodStr above, you can use both quotes safely by using the backslash \ as an escape character. Note The backslash \ should not be be confused with the forward slash /. They do not do the same thing.

Convert the assignments for a, b, and c to use the *= operator. var a = 5; var b = 12; var c = 4.6; // Only modify code below this line a *= 5; 3 *= b; c *= 10; a should equal 25 b should equal 36 c should equal 46 You should use the *= operator for each variable Do not modify the code above the line

The *= operator multiplies a variable by a number. myVar = myVar * 5; will multiply myVar by 5. This can be rewritten as: myVar *= 5; *Those variables should be coming before the integers when using the = property.

Convert the assignments for a, b, and c to use the /= operator. var a = 48; var b = 108; var c = 33; // Only modify code below this line a /= 12; b /= 4; c /= 11; a should equal 4 Passed b should equal 27 Passed c should equal 3 Passed You should use the /= operator for each variable Passed Do not modify the code above the line

The /= operator divides a variable by another number. myVar = myVar / 5; Will divide myVar by 5. This can be rewritten as: myVar /= 5;

Add the greater than operator to the indicated lines so that the return statements make sense. function testGreaterThan(val) { if (val > 100) { // Change this line return "Over 100"; } if (val > 10) { // Change this line return "Over 10"; } return "10 or Under"; } // Change this value to test testGreaterThan(10); testGreaterThan(0) should return "10 or Under" Passed testGreaterThan(10) should return "10 or Under" Passed testGreaterThan(11) should return "Over 10" Passed testGreaterThan(99) should return "Over 10" Passed testGreaterThan(100) should return "Over 10" Passed testGreaterThan(101) should return "Over 100" Passed testGreaterThan(150) should return "Over 100" Passed You should use the > operator at least twice

The greater than operator (>) compares the values of two numbers. If the number to the left is greater than the number to the right, it returns true. Otherwise, it returns false. Like the equality operator, greater than operator will convert data types of values while comparing. Examples 5 > 3 // true 7 > '3' // true 2 > 3 // false '1' > 9 // false

Add the greater than or equal to operator to the indicated lines so that the return statements make sense. function testGreaterOrEqual(val) { if (val >= 20) { // Change this line return "20 or Over"; } if (val >=10) { // Change this line return "10 or Over"; } return "Less than 10"; } // Change this value to test testGreaterOrEqual(10); testGreaterOrEqual(0) should return "Less than 10" Passed testGreaterOrEqual(9) should return "Less than 10" Passed testGreaterOrEqual(10) should return "10 or Over" Passed testGreaterOrEqual(11) should return "10 or Over" Passed testGreaterOrEqual(19) should return "10 or Over" Passed testGreaterOrEqual(100) should return "20 or Over" Passed testGreaterOrEqual(21) should return "20 or Over" Passed You should use the >= operator at least twice

The greater than or equal to operator (>=) compares the values of two numbers. If the number to the left is greater than or equal to the number to the right, it returns true. Otherwise, it returns false. Like the equality operator, greater than or equal to operator will convert data types while comparing. Examples 6 >= 6 // true 7 >= '3' // true 2 >= 3 // false '7' >= 9 // false

Add the inequality operator != in the if statement so that the function will return "Not Equal" when val is not equivalent to 99 // Setup function testNotEqual(val) { if (val !=99) { // Change this line return "Not Equal"; } return "Equal"; } // Change this value to test testNotEqual(10); testNotEqual(99) should return "Equal" Passed testNotEqual("99") should return "Equal" Passed testNotEqual(12) should return "Not Equal" Passed testNotEqual("12") should return "Not Equal" Passed testNotEqual("bob") should return "Not Equal" Passed You should use the != operator

The inequality operator (!=) is the opposite of the equality operator. It means "Not Equal" and returns false where equality would return true and vice versa. Like the equality operator, the inequality operator will convert data types of values while comparing. Examples 1 != 2 // true 1 != "1" // false 1 != '1' // false 1 != true // false 0 != false // false

Add the less than operator to the indicated lines so that the return statements make sense. function testLessThan(val) { if (val < 25) { // Change this line return "Under 25"; } if (val < 55) { // Change this line return "Under 55"; } return "55 or Over"; } // Change this value to test testLessThan(10); testLessThan(0) should return "Under 25" Passed testLessThan(24) should return "Under 25" Passed testLessThan(25) should return "Under 55" Passed testLessThan(54) should return "Under 55" Passed testLessThan(55) should return "55 or Over" Passed testLessThan(99) should return "55 or Over" Passed You should use the < operator at least twice

The less than operator (<) compares the values of two numbers. If the number to the left is less than the number to the right, it returns true. Otherwise, it returns false. Like the equality operator, less than operator converts data types while comparing. Examples 2 < 5 // true '3' < 7 // true 5 < 5 // false 3 < 2 // false '8' < 4 // false

Add the less than or equal to operator to the indicated lines so that the return statements make sense. function testLessOrEqual(val) { if (val <=12) { // Change this line return "Smaller Than or Equal to 12"; } if (val <=24) { // Change this line return "Smaller Than or Equal to 24"; } return "More Than 24"; } // Change this value to test testLessOrEqual(10); testLessOrEqual(0) should return "Smaller Than or Equal to 12" Passed testLessOrEqual(11) should return "Smaller Than or Equal to 12" Passed testLessOrEqual(12) should return "Smaller Than or Equal to 12" Passed testLessOrEqual(23) should return "Smaller Than or Equal to 24" Passed testLessOrEqual(24) should return "Smaller Than or Equal to 24" Passed testLessOrEqual(25) should return "More Than 24" Passed testLessOrEqual(55) should return "More Than 24" Passed You should use the <= operator at least twice

The less than or equal to operator (<=) compares the values of two numbers. If the number to the left is less than or equal to the number to the right, it returns true. If the number on the left is greater than the number on the right, it returns false. Like the equality operator, less than or equal to converts data types. Examples 4 <= 5 // true '7' <= 7 // true 5 <= 5 // true 3 <= 2 // false '8' <= 4 // false

Combine the two if statements into one statement which returns "Outside" if val is not between 10 and 20, inclusive. Otherwise, return "Inside". function testLogicalOr(val) { // Only change code below this line if (val >20 || val <10 ) { return "Outside"; } // Only change code above this line return "Inside"; } // Change this value to test testLogicalOr(15); You should use the || operator once Passed You should only have one if statement Passed testLogicalOr(0) should return "Outside" Passed testLogicalOr(9) should return "Outside" Passed testLogicalOr(10) should return "Inside" Passed testLogicalOr(15) should return "Inside" Passed testLogicalOr(19) should return "Inside" Passed testLogicalOr(20) should return "Inside" Passed testLogicalOr(21) should return "Outside" Passed testLogicalOr(25) should return "Outside"

The logical or operator (||) returns true if either of the operands is true. Otherwise, it returns false. The logical or operator is composed of two pipe symbols (|). This can typically be found between your Backspace and Enter keys. The pattern below should look familiar from prior waypoints: if (num > 10) { return "No"; } if (num < 5) { return "No"; } return "Yes"; will return "Yes" only if num is between 5 and 10 (5 and 10 included). The same logic can be written as: if (num > 10 || num < 5) { return "No"; } return "Yes";

Set remainder equal to the remainder of 11 divided by 3 using the remainder (%) operator. // Only change code below this line var remainder = 11%3;

The remainder operator % gives the remainder of the division of two numbers. Example 5 % 2 = 1 because Math.floor(5 / 2) = 2 (Quotient) 2 * 2 = 4 5 - 4 = 1 (Remainder) Usage In mathematics, a number can be checked to be even or odd by checking the remainder of the division of the number by 2. 17 % 2 = 1 (17 is Odd) 48 % 2 = 0 (48 is Even) Note The remainder operator is sometimes incorrectly referred to as the "modulus" operator. It is very similar to modulus, but does not work properly with negative numbers.

Read the values of the properties "an entree" and "the drink" of testObj using bracket notation and assign them to entreeValue and drinkValue respectively. // Setup var testObj = { "an entree": "hamburger", "my side": "veggies", "the drink": "water" }; // Only change code below this line var entreeValue = testObj["an entree"]; // Change this line var drinkValue = testObj["the drink"]; // Change this line entreeValue should be a string Passed The value of entreeValue should be "hamburger" Passed drinkValue should be a string Passed The value of drinkValue should be "water" Passed You should use bracket notation twice

The second way to access the properties of an object is bracket notation ([]). If the property of the object you are trying to access has a space in its name, you will need to use bracket notation. However, you can still use bracket notation on object properties without spaces. Here is a sample of using bracket notation to read an object's property: var myObj = { "Space Name": "Kirk", "More Space": "Spock", "NoSpace": "USS Enterprise" }; myObj["Space Name"]; // Kirk myObj['More Space']; // Spock myObj["NoSpace"]; // USS Enterprise Note that property names with spaces in them must be in quotes (single or double).

Add the strict inequality operator to the if statement so the function will return "Not Equal" when val is not strictly equal to 17 // Setup function testStrictNotEqual(val) { // Only Change Code Below this Line if (val !== 17) { // Only Change Code Above this Line return "Not Equal"; } return "Equal"; } // Change this value to test testStrictNotEqual(10); testStrictNotEqual(17) should return "Equal" Passed testStrictNotEqual("17") should return "Not Equal" Passed testStrictNotEqual(12) should return "Not Equal" Passed testStrictNotEqual("bob") should return "Not Equal" Passed You should use the !== operator

The strict inequality operator (!==) is the logical opposite of the strict equality operator. It means "Strictly Not Equal" and returns false where strict equality would return true and vice versa. Strict inequality will not convert data types. Examples 3 !== 3 // false 3 !== '3' // true 4 !== 3 // true

Add the equality operator to the indicated line so that the function will return "Equal" when val is equivalent to 12 // Setup function testEqual(val) { if (val ==12) { // Change this line return "Equal"; } return "Not Equal"; } // Change this value to test testEqual(10); testEqual(10) should return "Not Equal" Passed testEqual(12) should return "Equal" Passed testEqual("12") should return "Equal" Passed You should use the == operator

There are many Comparison Operators in JavaScript. All of these operators return a boolean true or false value. The most basic operator is the equality operator ==. The equality operator compares two values and returns true if they're equivalent or false if they are not. Note that equality is different from assignment (=), which assigns the value at the right of the operator to a variable in the left. function equalityTest(myVal) { if (myVal == 10) { return "Equal"; } return "Not Equal"; } If myVal is equal to 10, the equality operator returns true, so the code in the curly braces will execute, and the function will return "Equal". Otherwise, the function will return "Not Equal". In order for JavaScript to compare two different data types (for example, numbers and strings), it must convert one type to another. This is known as "Type Coercion". Once it does, however, it can compare terms as follows: 1 == 1 // true 1 == 2 // false 1 == '1' // true "3" == 3 // true

forgot to add

Read in the property values of testObj using dot notation. Set the variable hatValue equal to the object's property hat and set the variable shirtValue equal to the object's property shirt. // Setup var testObj = { "hat": "ballcap", "shirt": "jersey", "shoes": "cleats" }; // Only change code below this line var hatValue = testObj.hat; // Change this line var shirtValue = testObj.shirt; // Change this line hatValue should be a string Passed The value of hatValue should be "ballcap" Passed shirtValue should be a string Passed The value of shirtValue should be "jersey" Passed You should use dot notation twice

There are two ways to access the properties of an object: dot notation (.) and bracket notation ([]), similar to an array. Dot notation is what you use when you know the name of the property you're trying to access ahead of time. Here is a sample of using dot notation (.) to read an object's property: var myObj = { prop1: "val1", prop2: "val2" }; var prop1val = myObj.prop1; // val1 var prop2val = myObj.prop2; // val2

//This is an inline comment. /* This is a multi line comment */

There are two ways to write comments in JavaScript: Using // will tell JavaScript to ignore the remainder of the text on the current line: // This is an in-line comment. You can make a multi-line comment beginning with /* and ending with */: /* This is a multi-line comment */ Best Practice As you write code, you should regularly add comments to clarify the function of parts of your code. Good commenting can help communicate the intent of your code—both for others and for your future self.

Modify the data stored at index 0 of myArray to a value of 45. // Example var ourArray = [18,64,99]; ourArray[1] = 45; // ourArray now equals [18,45,99]. // Setup var myArray = [18,64,99]; // Only change code below this line. myArray[0] = 45; myArray should now be [45,64,99]. Passed You should be using correct index to modify the value in myArray.

Unlike strings, the entries of arrays are mutable and can be changed freely. Example var ourArray = [50,40,30]; ourArray[0] = 15; // equals [15,40,30] Note There shouldn't be any spaces between the array name and the square brackets, like array [0]. Although JavaScript is able to process this correctly, this may confuse other programmers reading your code.

Declare a local variable myVar inside myLocalScope. Run the tests and then follow the instructions commented out in the editor. Hint Refreshing the page may help if you get stuck. function myLocalScope() { 'use strict'; // you shouldn't need to edit this line var myVar="foo"; console.log(myVar); } myLocalScope(); // Run and check the console // myVar is not defined outside of myLocalScope No global myVar variable Passed Add a local myVar variable

Variables which are declared within a function, as well as the function parameters have local scope. That means, they are only visible within that function. Here is a function myTest with a local variable called loc. function myTest() { var loc = "foo"; console.log(loc); } myTest(); // logs "foo" console.log(loc); // loc is not defined loc is not defined outside of the function.

Create a variable called myData and set it to equal the first value of myArray using bracket notation. // Example var ourArray = [50,60,70]; var ourData = ourArray[0]; // equals 50 // Setup var myArray = [50,60,70]; // Only change code below this line. var myData = myArray[0]; The variable myData should equal the first value of myArray. Passed The data in variable myArray should be accessed using bracket notation.

We can access the data inside arrays using indexes. Array indexes are written in the same bracket notation that strings use, except that instead of specifying a character, they are specifying an entry in the array. Like strings, arrays use zero-based indexing, so the first element in an array is element 0. Example var array = [50,60,70]; array[0]; // equals 50 var data = array[1]; // equals 60 Note There shouldn't be any spaces between the array name and the square brackets, like array [0]. Although JavaScript is able to process this correctly, this may confuse other programmers reading your code.

Delete the "tails" property from myDog. You may use either dot or bracket notation. // Example var ourDog = { "name": "Camper", "legs": 4, "tails": 1, "friends": ["everything!"], "bark": "bow-wow" }; delete ourDog.bark; // Setup var myDog = { "name": "Happy Coder", "legs": 4, "tails": 1, "friends": ["freeCodeCamp Campers"], "bark": "woof" }; // Only change code below this line. delete myDog.tails; Delete the property "tails" from myDog. Passed Do not modify the myDog setup

Web Development Chapter 8 (JavaScript)

Ensembles d'études connexes

life of PI test

BIO 106 - The Chemistry of Life: Chapters 1-5

Unit 3 - Executive branch

Final Exam Review (Positive Psychology)

Chapter 6 SB

MKT 3013 Study Questions

Study Guide

Unit 3 Test

Digital Marketing Exam

Aldi NLU codes

NISSAN INTELLIGENT LANE INTERVENTION

Chapter Eight

BIO 320 Q2

apush ch. 14

ESC Exam #3

Hitler's Germany

MGMT 309 - Chapter 5

Prep Quiz #7 - Endocrine drugs

Ch. 10 End of Chapter Questions

A chem Ch 31-34