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Array

A contiguous, index-based collection of elements stored in a single block of memory.

Since ES2024 Spec ↗

Syntax

const arr = new Array(length);  // or array literal []

Parameters

NameTypeRequiredDescription
length number No Optional initial length of the array. If omitted, an empty array is created; elements can be pushed at any time.

Returns

Array — A new Array instance.

Examples

const nums = [10, 20, 30, 40, 50];
console.log(nums[2]);          // random access O(1)
nums.push(60);
console.log(nums.length);
Output 
30
6

const sparse = new Array(5).fill(0);
sparse[2] = 99;
console.log(sparse);
Output 
[ 0, 0, 99, 0, 0 ]

Notes

| Operation | Best | Avg | Worst | Space | |---------------|------|------|-------|-------| | Access by idx | O(1) | O(1) | O(1) | O(n) | | Search | O(1) | O(n) | O(n) | O(1) | | Insert (end) | O(1) | O(1) | O(n)* | O(1) | | Insert (mid) | O(n) | O(n) | O(n) | O(1) | | Delete (end) | O(1) | O(1) | O(1) | O(1) | | Delete (mid) | O(n) | O(n) | O(n) | O(1) | *O(n) worst case for push when internal buffer must be resized. JavaScript `Array` is dynamic and can hold mixed types. For typed numeric data prefer `Int32Array` / `Float64Array` (TypedArrays) which store values in a true contiguous buffer.

See also