Skip to main content

require-array-sort-compare

Require Array#sort and Array#toSorted calls to always provide a compareFunction.

💭

This rule requires type information to run, which comes with performance tradeoffs.

When called without a compare function, Array#sort() and Array#toSorted() converts all non-undefined array elements into strings and then compares said strings based off their UTF-16 code units [ECMA specification].

The result is that elements are sorted alphabetically, regardless of their type. For example, when sorting numbers, this results in a "10 before 2" order:

[1, 2, 3, 10, 20, 30].sort(); //→ [1, 10, 2, 20, 3, 30]

This rule reports on any call to the sort methods that do not provide a compare argument.

eslint.config.mjs
export default tseslint.config({
  rules: {
    "@typescript-eslint/require-array-sort-compare": "error"
  }
});

Try this rule in the playground ↗

Examples​

This rule aims to ensure all calls of the native sort methods provide a compareFunction, while ignoring calls to user-defined methods.

const array: any[];
const stringArray: string[];

array.sort();

// String arrays should be sorted using `String#localeCompare`.
stringArray.sort();
Open in Playground

Options​

This rule accepts the following options:

type Options = [
  {
    /** Whether to ignore arrays in which all elements are strings. */
    ignoreStringArrays?: boolean;
  },
];

const defaultOptions: Options = [{ ignoreStringArrays: true }];

ignoreStringArrays​

Whether to ignore arrays in which all elements are strings. Default: true.

Examples of code for this rule with { ignoreStringArrays: true }:

const one = 1;
const two = 2;
const three = 3;
[one, two, three].sort();
Open in Playground

When Not To Use It​

If you intentionally want your arrays to be always sorted in a string-like manner, you can turn this rule off safely.

Type checked lint rules are more powerful than traditional lint rules, but also require configuring type checked linting.

See Troubleshooting > Linting with Type Information > Performance if you experience performance degradations after enabling type checked rules.

Resources​