Arrays

index

a position in an array

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)

How can we get the length of an array arr?

arr.length

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

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

Model complexity vs running time

the simpler the model, the faster it runs the more complex, the more computing power needed, takes longer

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();

var groceries = ["milk", "eggs", "bread", "cheese", "yogurt", "sugar"]; What will be the result of groceries.indexOf("yogurt"); ?

4

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 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]

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