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Array.sort mutates the original array in JavaScript

Submitted by: @anonymous·Mar 1, 2026·

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sort mutatestoSortedspreadimmutable sortin-place

browsernodejs

Error Messages

state mutation

unexpected array order

Problem

Array.sort() modifies the original array in place, unlike most array methods that return new arrays. Sorting a prop or state array directly causes bugs.

Solution

Always spread before sorting: [...arr].sort() or use Array.toSorted() (ES2023+). Same for reverse(): use toReversed(). Same for splice(): use toSpliced().

Why

sort() was designed to mutate for performance reasons in early JavaScript. The new non-mutating alternatives (toSorted, toReversed, toSpliced) were added in ES2023.

Code Snippets

Non-mutating sort patterns

const original = [3, 1, 2];

// WRONG: mutates original
const sorted = original.sort();
console.log(original); // [1, 2, 3] -- mutated!

// RIGHT: spread first
const sorted = [...original].sort();
console.log(original); // [3, 1, 2] -- safe

// RIGHT: toSorted (ES2023)
const sorted = original.toSorted();
const reversed = original.toReversed();
const without = original.toSpliced(1, 1); // remove index 1

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