58 lines
2.1 KiB
Markdown
58 lines
2.1 KiB
Markdown
|
# Selector Specificity
|
||
|
|
||
|
[<img alt="npm version" src="https://img.shields.io/npm/v/@csstools/selector-specificity.svg" height="20">][npm-url]
|
||
|
[<img alt="Build Status" src="https://github.com/csstools/postcss-plugins/workflows/test/badge.svg" height="20">][cli-url]
|
||
|
[<img alt="Discord" src="https://shields.io/badge/Discord-5865F2?logo=discord&logoColor=white">][discord]
|
||
|
|
||
|
## Usage
|
||
|
|
||
|
Add [Selector Specificity] to your project:
|
||
|
|
||
|
```bash
|
||
|
npm install postcss @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._
|
||
|
|
||
|
### Comparing
|
||
|
|
||
|
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](https://github.com/keeganstreet/specificity)
|
||
|
- [bramus/specificity](https://github.com/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
|
||
|
|
||
|
[Selector Specificity]: https://github.com/csstools/postcss-plugins/tree/main/packages/selector-specificity
|