Arrays | Ucode

Appearance

On this page

Arrays ​

JavaScript's Array can contain any data type and access each element via index.

To get the length of an Array, simply access the length property:

javascript
let arr = [1, 2, 3.14, 'Hello', null, true];
console.log(arr.length); // 6

Assigning a new value to the length property directly will change the size of the Array:

javascript
let arr = ['A', 'B', 'C'];
arr.length = 6; // arr becomes ['A', 'B', 'C', undefined, undefined, undefined]
arr.length = 2; // arr becomes ['A', 'B']

You can modify an Array element via its index:

javascript
let arr = ['A', 'B', 'C'];
arr[1] = 99; // arr now becomes ['A', 99, 'C']

If you assign a value to an index that exceeds the current range, it will also adjust the Array size:

javascript
let arr = ['A', 'B', 'C'];
arr[5] = 'x'; // arr becomes ['A', 'B', 'C', undefined, undefined, 'x']

indexOf ​

Similar to String, Array can use indexOf() to find the position of a specified element:

javascript
let arr = [10, 20, '30', 'xyz'];
arr.indexOf(10); // returns 0
arr.indexOf(30); // returns -1

slice ​

slice() extracts a portion of an Array and returns a new one:

javascript
let arr = ['A', 'B', 'C', 'D', 'E', 'F', 'G'];
arr.slice(0, 3); // returns ['A', 'B', 'C']

push and pop ​

push() adds elements to the end, while pop() removes the last element:

javascript
let arr = [1, 2];
arr.push('A', 'B'); // arr becomes [1, 2, 'A', 'B']
arr.pop(); // returns 'B'

unshift and shift ​

unshift() adds elements to the front, while shift() removes the first element:

javascript
let arr = [1, 2];
arr.unshift('A', 'B'); // arr becomes ['A', 'B', 1, 2]

sort ​

sort() modifies the Array in place to sort elements:

javascript
let arr = ['B', 'C', 'A'];
arr.sort(); // arr becomes ['A', 'B', 'C']

reverse ​

reverse() reverses the order of elements:

javascript
let arr = ['one', 'two', 'three'];
arr.reverse(); // arr becomes ['three', 'two', 'one']

splice ​

splice() modifies the Array by removing and adding elements:

javascript
let arr = ['Microsoft', 'Apple', 'Yahoo'];
arr.splice(1, 1, 'Google'); // arr becomes ['Microsoft', 'Google', 'Yahoo']

concat ​

concat() merges two Arrays and returns a new one:

javascript
let arr = ['A', 'B', 'C'];
let added = arr.concat([1, 2, 3]); // returns ['A', 'B', 'C', 1, 2, 3]

join ​

join() connects all elements into a string:

javascript
let arr = ['A', 'B', 'C', 1, 2, 3];
arr.join('-'); // returns 'A-B-C-1-2-3'

Multi-dimensional Arrays ​

An element of an Array can be another Array, creating multi-dimensional arrays:

javascript
let arr = [[1, 2, 3], [400, 500, 600], '-'];

Summary ​

Array provides a way to store a sequence of elements, accessible by index.