dataStructures

<

start

>

clear

copy to:

0

insert

save as:

new page

new last

delete

<

start

>

last

Go to

0

Question

Data Structures: Lists, Dictionaries, and Strings

Variables hold individual values, but sometimes we want to easily deal with a bunch of related values, and pass them around as a unit.  The most common ways to do that are with Lists, Dictionaries, and Strings

A List is just a list of values.  They are created by putting the list in angle brackets, like this:

myList = [1, 2, 3]
myList

You can get individual elements of a list  by asking for them by index:

myList[1]

As you can see, the first element of a list  is always at position 0:

myList[0]

Asking for a list  element out of bounds always returns undefined

myList[-1]
myList[4]
myList['a']

The length of a list is always given by its 'length' property

myList.length

So the last element is always given by its length - 1

myList[myList.length - 1]

What goes inside the square brackets to index a list is any expression at all

i = 1
myList[i + 1]

Which makes it easy to (for example) perform computations on a list

sum = 0
for(var i = 0; i < myList.length; i++) {
    sum = sum + myList[i]
}
sum

You can assign to any element of a list:

myList[2] = 4
myList

or add elements to the end with push()

myList.push(5)
myList

We can take elements off the end with pop(), which returns the element popped:

myList.pop()
myList