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Array Basics

Array data structures are going to share similar functionality between all languages.

The syntax for a js array is going to look familiar to that of a traditional Java array, the major exception being that they are not typed.

It functions, however, in a manner more similarly to that of an ArrayList.

JS arrays actually have a number of functions tied to their class that allow them to be an extremely versatile data structure.

Creating Arrays

To create a new array literal with no starting values, we simply use [] 

let nums = [];

If we instead wanted to create an array with values, we could list the values separated by a comma. 

let nums = [1,2,3,4];
let names = ["Andrew", "Kris"];

Accessing Properties and Values

Once an array has been created we can check how many elements are stored inside of it with the .length property. 

let nums = [1,2,3,4];
nums.length;     // 4

To access a specific element in an array we can use subscript notation, just like in Java. 

let nums = [1,2,3,4];
nums[2];         // 3

Adding to an Array push(value)

Add an item to the end of an Array and return the resulting length of the Array.

let arr = [1,2,3];
arr.push('kiwi'); // 4

arr; // [1,2,3,'kiwi']

Skill Drill

  • Create a folder ArrayHandsOn in SD/JS. Inside of this location create an array.js file and an array.html file. We will use this file for all of the hands ons in this chapter.

  • Assign an empty array to a variable named classmates.

  • Use push() to add the names of your classmates to the array.

Removing from an Array pop()

Remove and return the last item in an Array.

let arr = [1,2,3,4];
arr.pop(); // 4

arr; // [1,2,3]

Skill Drill

  • Use pop() to store the last name from your classmates array into a variable named last.

  • Use console.log to print out last, and use another console.log to print out the classmates array.

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