N341 Chapters
strict not equal to
!==
Which of the following is a truthy value?
"false" 167
logical and
The && operator used to form a compound Boolean expression
var myPhone = new Object();
empty object
Which of the following is NOT a type of JavaScript operator?
sign operator
The Document Object Model (DOM) _____. Correct Answer
specifies how the browser should make a model of the html page Correct Answer is a tree-like structure specifies how JavaScript can change the html page
Check each line of code that correctly sets strMessage to a string value:
strMessage = 'Sally said, "hello!" '; strMessage = "Sally said, \"hello!\" ";
var strMessage = 'Hello World';
strMessage can use the built-in properties and methods of the String object. r strMessage.length returns the length of the message - which is 11
The break keyword tells the JavaScript interpreter _____ .
that is has finished with a switch statement to go to the first line of code that appears after a loop or switch statement
A switch statement works like a series of if statements. The difference is that the switch statement performs more quickly.
true
A unary operator returns a result using just one operand.
true
After a DOM query, if your script needs to use the result more than once, it is a good idea to store the location of the element(s) in a variable. This is known as caching the selection.
true
Event listeners are not supported in some older browsers, so it is necessary to provide fallback code if support for those browsers is necessary. Correct Answer
true
Multi-line comments start with /* and end with */. These comments can span many lines and are often used to describe how the script works.
true
he Math object _____.
Correct Answer is used with the name of the Math object followed by the needed property or method. For example, numTwo = Math.sqrt(4); Correct Answer has a method that generates a random number Correct Answer is a global object
The keyword this ______?
Correct Answer refers to the window object when used in a global context Correct Answer usually refers to the object in which the function operates. Correct Answer has a value that changes in different situations.
do while
Correct Answercode needs to run at least once
HTML attribute; Old technology - DO NOT USE
HTML Event Handler
There are two very different approaches to changing content on a DOM tree: [ Select ] property and DOM manipulation. [ Select ] easily targets individual nodes in the DOM tree, whereas [ Select ] is better suited to updating entire fragments.
INNERHTML DOM manipulation
var intA = 1; // first operand in the condition var intB = 2; // second operand in the condition var intC = 3; // third operand in the condition if (!(intA < intB)) { doStuff(); } // end if
In the example above, doStuff() will _____. never be called
In JavaScript, what does the operator ++ do?
It adds one to the current number.
In JavaScript, what does the operator + do?
It adds two numbers. It concatenates two strings.
Choose 3 correct statements for type coercion? Correct Answer
It creates a need for using strict equality operators Correct Answer It can lead to errors. Correct Answer It can lead to unexpected values in your code
Which two of the following steps must be completed to add an element to the page using DOM manipulation?
Add the element to the DOM - appendChild() Correct Answer Create the element - createElement()
events occur when the user interacts with the browser's UI rather than the web page.
User Interface (UI)
Which of the following are focus & blur events?
blur focusout Correct Answer focusin Correct Answer focus
When evaluating a condition with a comparison operator, the result will be a _____.
boolean
Properties and methods of an object are accessed using _____.
dot notation
document.write()
easy way for beginners to learn to add content to a page using this technique after the page has loaded can cause it to overwrite the entire page
If an HTML page contained a 8x8 table of nodes, creating an event handler for each of the 64 nodes could slow down the page. Fortunately, event flow allows JavaScript to listen for an event on a parent element. A single listener can be created on the parent element, and the event object's target property can be used to determine which node of the table was clicked. The process of creating a single listener on a parent event is called _____.
event delegation
All JavaScript element selection methods are supported equally well in every major browser.
false
An array can be a list of numbers or strings, but not a list of objects.
false
Writing comments inside a script is a way to explain what the code is doing. The JavaScript interpreter carefully reads each comment to get detailed information.
false
A series of statements that have been grouped together to form a specific task is called _____.
ffunction
A function that appears where the interpreter expects to see an expression is called a _____
function expression
TEXTcONTENT
gets or sets only text from the containing element
innerHTML
gets or sets text & markup but has security risks
A variable that is declared outside a function can be used anywhere in the script. It is called a _____ variable and has _____ scope.
global globa
When an event has occurred, it is said to [ Select ] . Events are said to [ Select ] a function or script. When it is indicated which event will cause a response on a selected node, it is said to [ Select ] an event to a DOM node.
have fired or have been raised trigger bind
Objects _____.
have functions that become known as methods Correct Answer group together a set of variables and functions Correct Answer create a model of something you would recognize from the real world Correct Answer have variables that become known as properties
Within an object, the value of a property can be a _____.
Correct Answer Array Correct Answer Number Correct Answer Boolean Correct Answer String Correct Answer another object
To use the built-in Date object in JavaScript, it is necessary to create an instance of the Date object using the constructor method.
Correct Answer True
Using global variables can lead to errors and slowly performing scripts because _____.
Correct Answer global variables can have naming collisions with other scripts Correct Answer global variables use more memory than local variables
does not work with IE8 or earlier; can attach multiple functions to an event
DOM Level 2 Event Listener
The following line of code sets a variable to a numeric value:
intQuantity = 7;
Correct Answer An array
is a list of values. It is helpful for storing a list of related items.
keyboard events
keypress, keydown, keyup input
var myPhone = {};
literal notation
To access the elements on the DOM tree, JavaScript can be used to select _____.
multiple nodes by class Correct Answer using CSS selector syntax Correct Answer an individual node by element id Correct Answer multiple nodes by tag name
events occur when the DOM structure has been changed by a script.
mutation
Three data types that JavaScript uses are
numeric string boolean
You Answered Document Object Model Correct Answer
page title, last modification date, getElementById() method
Global JavaScript Objects Correct Answe
rString, Number, Math, and Date objects
The response that a function provides when it is called is a _____.
return
The location of a variable declaration will affect where it can be used within the code. This is known as the variable's _____.
scope
Event handling involves three steps. Put these steps in the order they must appear in the code.
select element node bind an event to node specify code that is to run
Each individual instruction in a script is known as a statement. Statements should end in a ____. This allows both the human and the computer to understand the code.
semicolon
When an event occurs, the event object tells _____.
the type of event that was fired Correct Answer information about the event information about the element that triggered the event
strong support in all major browsers; can only attach a single function to an event
traditional DOM event handler
A DOM query can return either one element or a collection of nodes.
true
Once an element node is selected, it is possible to select other nodes related to it. This is called traversing the DOM. New elements can be selected based on their relationship as a parent, sibling, or child of the originally selected element.
true
Once an element node or group of nodes is selected, the attributes, the child elements, and the text content can be changed.
true
Operators and expressions allow programmers to create a single value from one or more values.
true
Single-line comments begin with two forward slash characters. They are usually used to provide short descriptions of what the code is doing.
true
Some browsers treat whitespace between elements as a text node. So, a DOM query can return different elements in different browsers.
true
The preventDefault() method of the event object changes the default behavior of an element. This can be used to keep the user on the page after clicking on a link.
true
Two essential steps to using variables are to declare them and to assign them a value.
true
In JavaScript, the _____ keyword is used to declare variables.
var
Computers use _____ to store data for use in computations or for later reference.
variables
Browser Object Model You Answered
window location, scrolling distance, and alert() method
logical or
||
strict equal to
===
main types of DOM nodes?
The Document Node Correct Answer Element Nodes Correct Answer Attribute Nodes Correct Answer Text Nodes
The following rules apply when giving a variable a name.
The name must not contain a dash or a period. Correct Answer The name must not start with a number. Correct Answer All variables are case sensitive
var intA = 1; // first operand in the condition var intB = 2; // second operand in the condition var intC = 3; // third operand in the condition if (place condition here) { doStuff(); } // end if
Which expression will NOT allow the function doStuff() to be called? intA>=int B
The following line of code sets a variable to a Boolean value:
blnIsBlue = true;
falsy value
a variable with no value assigned to it
Cross-Site Scripting Attacks (XSS) involve an attacker placing malicious code into a site. Using the innerHTML property to allow user input is one way to enable these attacks. XSS can allow an attacker to _____. Correct Answer
access the site's cookies Correct Answer post unwanted content Correct Answer spread malicious code Correct Answer make purchases with the user's account Correct Answer access the user's login information Correct Answer access form data
strColors = ['red', 'white', 'blue']; Correct Answer
an array literal
To organize your data, you can either use an array or use an object to group a set of related values. If the order of the items is important, it is better to use an _____.
array
var strColors = new Array('red', 'white', 'blue');
array constructor
If different parts of a script need to perform the same task, writing a function will _____.
avoid unnecessarily repetitive code Correct Answer keep the code shorter Correct Answer make the script easier to read
dom mainpulation
best technique to use when changing one element that has many siblings if many changes are needed, it needs more code and is slower than other methods does not affect event handlers
element.innerHTML
can be used to add lots of new markup using less code than other options simple way to remove all content from one element (by assigning it a blank string)
When creating lots of objects with similar functionality, it is good to use _____.
constructor notation
var myPhone = new Phone(ꞌmobileꞌ, ꞌ3175551212ꞌ, 200);
constructor notation
Two keywords that are often used with loops are:
continue break
Sections of statements called code blocks are surrounded by _____. This creates a group of statements and helps to make scripts more readable.
curly braces
Which loop has the statements in the code block before the condition?
do while
var intA = 1; // first operand in the condition var intB = 2; // second operand in the condition var intC = 3; // third operand in the condition var intD = 4; // fourth operand in the condition if ( (intA < intB) || (intC > intD) ) { doStuff(); } // end if else { doDifferentStuff(); } //end else
doStuff() is always called. Correct Answer the condition (intC > intD) is not checked