JavaScript Arrays
What is an array?
Let's say, you have 3 users and you want to store their names:
const user1 = 'A';
const user2 = 'B';
const user3 = 'C';
What if you have 100? It will be 100 lines of codes.
Instead, we can store in an array
like this:
const users = ['A', 'B', 'C', ...];
Creating an array
To create an array, we use the square bracket []
.
Array can store any type of values.
// Array of strings
const names = ['A', 'B', 'C'];
// Array of numbers
const heights = [150, 160, 170];
// Array of objects
const users = [
{ id: 1, name: 'A' },
{ id: 2, name: 'B' },
];
And more... we will talk about Object
in future sections.
Accessing an element
Element
means the individual value in the array
.
const names = ['A', 'B', 'C'];
A, B, and C are all called element
in the names array
.
We access the element by their position
in that array. Note that in JavaScript
and most of the programming languages, array starts with index 0
.
const names = ['A', 'B', 'C'];
console.log(names[0]); // output: A
console.log(names[1]); // output: B
console.log(names[2]); // output: C
Changing an element
const names = ['A', 'B', 'C'];
names[0] = 'D';
console.log(names); // output: ['D', 'B', 'C']
Array methods
In JavaScript, there are tons of array methods. Here are some common ones, you can explore more here:
Array.length
- Get array's length
const nums = [1, 2, 3];
console.log(nums.length); // output: 3
Array.push
- Add new element into array
const nums = [1, 2, 3];
nums.push(4);
console.log(nums); // output: [1, 2, 3, 4]
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