Selector Specificity [][postcss]

[][npm-url]
[][cli-url]
[][discord]

Usage

Add [Selector Specificity] to your project:

``bash
npm install @csstools/selector-specificity --save-dev
`

`js
import parser from 'postcss-selector-parser';
import { selectorSpecificity } from '@csstools/selector-specificity';

const selectorAST = parser().astSync('#foo:has(> .foo)');
const specificity = selectorSpecificity(selectorAST);

console.log(specificity.a); // 1
console.log(specificity.b); // 1
console.log(specificity.c); // 0
`

_selectorSpecificity takes a single selector, not a list of selectors (not : a, b, c).
To compare or otherwise manipulate lists of selectors you need to call selectorSpecificity on each part._

$3

The package exports a utility function to compare two specificities.

`js
import { selectorSpecificity, compare } from '@csstools/selector-specificity';

const s1 = selectorSpecificity(ast1);
const s2 = selectorSpecificity(ast2);
compare(s1, s2); // -1 | 0 | 1
`

- if s1 < s2 then compare(s1, s2) returns a negative number (< 0)
- if s1 > s2 then compare(s1, s2) returns a positive number (> 0)
- if s1 === s2 then compare(s1, s2) returns zero (=== 0)

Prior Art

- keeganstreet/specificity
- bramus/specificity

For CSSTools we always use postcss-selector-parser` and want to calculate specificity from this AST.

[cli-url]: https://github.com/csstools/postcss-plugins/actions/workflows/test.yml?query=workflow/test
[discord]: https://discord.gg/bUadyRwkJS
[npm-url]: https://www.npmjs.com/package/@csstools/selector-specificity
[postcss]: https://github.com/postcss/postcss

[Selector Specificity]: https://github.com/csstools/postcss-plugins/tree/main/packages/selector-specificity