Requires Array#sort
calls to always provide a compareFunction
(require-array-sort-compare
)
This rule prevents invoking the Array#sort()
method without providing a compare
argument.
When called without a compare function, Array#sort()
converts all non-undefined array elements into strings and then compares said strings based off their UTF-16 code units.
The result is that elements are sorted alphabetically, regardless of their type. When sorting numbers, this results in the classic "10 before 2" order:
[1, 2, 3, 10, 20, 30].sort(); //โ [1, 10, 2, 20, 3, 30]
This also means that Array#sort
does not always sort consistently, as elements may have custom #toString
implementations that are not deterministic; this trap is noted in the language specification thusly:
note
Method calls performed by the ToString
abstract operations in steps 5 and 7 have the potential to cause SortCompare
to not behave as a consistent comparison function.
https://www.ecma-international.org/ecma-262/9.0/#sec-sortcompare
Rule Details
This rule aims to ensure all calls of the native Array#sort
method provide a compareFunction
, while ignoring calls to user-defined sort
methods.
Examples of code for this rule:
- โ Incorrect
- โ Correct
const array: any[];
const stringArray: string[];
array.sort();
// String arrays should be sorted using `String#localeCompare`.
stringArray.sort();
const array: any[];
const userDefinedType: { sort(): void };
array.sort((a, b) => a - b);
array.sort((a, b) => a.localeCompare(b));
userDefinedType.sort();
Options
The rule accepts an options object with the following properties:
type Options = {
/**
* If true, an array which all elements are string is ignored.
*/
ignoreStringArrays?: boolean;
};
const defaults = {
ignoreStringArrays: false,
};
ignoreStringArrays
Examples of code for this rule with { ignoreStringArrays: true }
:
- โ Incorrect
- โ Correct
const one = 1;
const two = 2;
const three = 3;
[one, two, three].sort();
const one = '1';
const two = '2';
const three = '3';
[one, two, three].sort();
When Not To Use It
If you understand the language specification enough, you can turn this rule off safely.
Attributes
- โ Recommended
- ๐ง Fixable
- ๐ญ Requires type information