arrayMutableSorts

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

✅ This rule is included in the ts stylistic and stylisticStrict presets.

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.

const 
const values: number[]
values = [3, 1, 2];
const 
const sorted: number[]
sorted = 
const values: number[]
values.
Array<number>.sort(compareFn?: ((a: number, b: number) => number) | undefined): number[]
Sorts an array in place.
This method mutates the array and returns a reference to the same array.
@param ― 
compareFn Function used to determine the order of the elements. It is expected to return
a negative value if the first argument is less than the second argument, zero if they're equal, and a positive
value otherwise. If omitted, the elements are sorted in ascending, UTF-16 code unit order.
[11,2,22,1].sort((a, b) => a - b)
sort();

const 
const items: number[]
items = [3, 1, 2];
const 
const sorted: number[]
sorted = 
const items: number[]
items.
Array<number>.sort(compareFn?: ((a: number, b: number) => number) | undefined): number[]
Sorts an array in place.
This method mutates the array and returns a reference to the same array.
@param ― 
compareFn Function used to determine the order of the elements. It is expected to return
a negative value if the first argument is less than the second argument, zero if they're equal, and a positive
value otherwise. If omitted, the elements are sorted in ascending, UTF-16 code unit order.
[11,2,22,1].sort((a, b) => a - b)
sort((
a: number
a, 
b: number
b) => 
a: number
a - 
b: number
b);

const 
const data: number[]
data = [3, 1, 2];
const 
const result: number[]
result = [...
const data: number[]
data].
Array<number>.sort(compareFn?: ((a: number, b: number) => number) | undefined): number[]
Sorts an array in place.
This method mutates the array and returns a reference to the same array.
@param ― 
compareFn Function used to determine the order of the elements. It is expected to return
a negative value if the first argument is less than the second argument, zero if they're equal, and a positive
value otherwise. If omitted, the elements are sorted in ascending, UTF-16 code unit order.
[11,2,22,1].sort((a, b) => a - b)
sort();

const 
const values: number[]
values = [3, 1, 2];
const 
const sorted: any
sorted = 
const values: number[]
values.toSorted();Error ts(2550)  ― Property 'toSorted' does not exist on type 'number[]'. Do you need to change your target library? Try changing the 'lib' compiler option to 'es2023' or later.

const 
const items: number[]
items = [3, 1, 2];
const 
const sorted: any
sorted = 
const items: number[]
items.toSorted((
a: any
a, 
b: any
b) => 
a: any
a - 
b: any
b);Error ts(2550)  ― Property 'toSorted' does not exist on type 'number[]'. Do you need to change your target library? Try changing the 'lib' compiler option to 'es2023' or later.

const 
const values: number[]
values = [3, 1, 2];
const values: number[]
values.
Array<number>.sort(compareFn?: ((a: number, b: number) => number) | undefined): number[]
Sorts an array in place.
This method mutates the array and returns a reference to the same array.
@param ― 
compareFn Function used to determine the order of the elements. It is expected to return
a negative value if the first argument is less than the second argument, zero if they're equal, and a positive
value otherwise. If omitted, the elements are sorted in ascending, UTF-16 code unit order.
[11,2,22,1].sort((a, b) => a - b)
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.

Equivalents in Other Linters

ESLint: unicorn/no-array-sort

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arrayMutableSorts

Examples

Options

When Not To Use It

Further Reading

Equivalents in Other Linters