arrayMutableSorts

Reports .sort() calls on arrays that mutate the original array.

✅ This rule is included in the ts stylistic preset.

The .sort() method mutates the original array in place. Using .toSorted() instead returns a new sorted array without modifying the original, making code more predictable and avoiding unintended side effects.

Examples

❌ Incorrect

const values = [3, 1, 2];
const sorted = values.sort();

const items = [3, 1, 2];
const sorted = items.sort((a, b) => a - b);

const data = [3, 1, 2];
const result = [...data].sort();

✅ Correct

const values = [3, 1, 2];
const sorted = values.toSorted();

const items = [3, 1, 2];
const sorted = items.toSorted((a, b) => a - b);

const values = [3, 1, 2];
values.sort();

Options

This rule is not configurable.

When Not To Use It

If you intentionally want to mutate the original array in place, or if you’re working in an environment that doesn’t support .toSorted() (ES2023+), you may want to disable this rule. Note that .sort() is still allowed when used as a standalone expression statement since the mutation is likely intentional in that case.

Further Reading

• MDN: Array.prototype.sort()
• MDN: Array.prototype.toSorted()

Equivalents in Other Linters

• ESLint: unicorn/no-array-sort