Arrays
index
a position in an array
How can we get the length of an array arr?
arr.length
To add all numbers in an array
create a variable sum : var sum = 0; create a for loop, add each element to the sum: for(var i = 0; i<arr.length; i++){ var cur= arr[i]; sum+=cur; } println(sum); }
Which loop will correctly loop over the array arr and print each value inside of it?
for(var i = 0; i < arr.length; i++){ var curr = arr[i]; println(curr); }
What method can we use to find the index of a particular element in an array?
indexOf
What index refers to the "end" of an array?
the highest index
how to make an empty array
var arr= [ ]; square brackets empty
How to create an array?
var arr= [1,2,3,4,5] ; var shoppingList= ["bread", "eggs", "milk"];
How to get array length (# items in an array)?
var length= arr.length; arr is name of the array if you had an array called shoppingList: var length= shoppingList.length;
var numbers = [0, 1, 2, 3, 4, 5]; How can we remove the last item from the end of the numbers array and store it in a variable called value?
var value = numbers.pop();
model
A set of simplifying assumptions about some aspect of the real world.
What is a benefit of a simulation?
mimics real world events without cost or danger
var numbers = [0, 1, 2, 3, 4]; How can we add a 5 to the end of numbers?
numbers.push(5);
to print an item in an array
println(arr[0]) prints the item at index 0 of arr
How to change an index of an array?
shoppingList[2] = "cake" ; changes the item at index 2 to cake
var shoppingList = ["milk", "eggs", "sugar", "bread", "cake"]; Which line of code will correctly change "cake" to "apples"?
shoppingList[4] = "apples";
var groceries = ["milk", "eggs", "bread", "cheese", "yogurt", "sugar"]; What will be the result of groceries.indexOf("cake"); ?
-1, when an item doesn't exist in the array, the index is returned as -1
What does Javascript index start at vs AP lang start?
AP- index starts at 1 JAVA- index starts 0
What is an array (or list)?
An ordered collection of items
How to print every element in an array?
First have the array created: var arr= ["bread", "milk", "cookies", "cheese"]; then create a for loop: for(var i = 0; i< arr.length; i++){ var cur= arr[i]; println(cur); }
Which of the following statements are true about simulation models? I - Models often omit unnecessary features of the phenomena being modeled.II - The time it takes for a simulation to run increases as the underlying model becomes more complex.
I and II
var groceries = ["milk", "eggs", "bread", "cheese", "yogurt", "sugar"]; What will be the result of groceries.indexOf("yogurt"); ?
4
What is the output of the following program? function start(){ var arr = [1, 2, 3, 4, 5, 6, 7]; var elem = arr.pop(); println(arr); println(elem); }
[1, 2, 3, 4, 5, 6] 7
What is the output of the following program? function start(){ var arr = [1, 2, 3, 4, 5, 6, 7]; var elem = arr.remove(2); println(arr); }
[1, 2, 4, 5, 6, 7]
simulation
an imitation of a possible situation
What kinds of items can we store in arrays?
any kind of object (anything you can store in a variable)
to remove the last element in the array
arr.pop( ); you dont need to put anything in parenthesis if you save the popped item into a variable, you can access it later ex) var last = arr.pop( );
How to add an element to the array?
arr.push( ); whatever you want to add to the end of list put in ( ). for example if you want to add cake to the 0 index arr.push("cake"); arr.push("bread"); now index 0= cake and index 1 = bread
How to remove 1 element?
arr.remove(i); i=index arr.remove(2); removes element at index 2
How to remove at a certain index one or more?
arr.splice(2,1); remove starting from index 2, 1 element
Model complexity vs running time
the simpler the model, the faster it runs the more complex, the more computing power needed, takes longer