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57 lines
2.1 KiB
57 lines
2.1 KiB
# Selector Specificity |
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[<img alt="npm version" src="https://img.shields.io/npm/v/@csstools/selector-specificity.svg" height="20">][npm-url] |
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[<img alt="Build Status" src="https://github.com/csstools/postcss-plugins/workflows/test/badge.svg" height="20">][cli-url] |
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[<img alt="Discord" src="https://shields.io/badge/Discord-5865F2?logo=discord&logoColor=white">][discord] |
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## Usage |
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Add [Selector Specificity] to your project: |
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```bash |
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npm install postcss @csstools/selector-specificity --save-dev |
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``` |
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```js |
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import parser from 'postcss-selector-parser'; |
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import { selectorSpecificity } from '@csstools/selector-specificity'; |
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const selectorAST = parser().astSync('#foo:has(> .foo)'); |
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const specificity = selectorSpecificity(selectorAST); |
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console.log(specificity.a); // 1 |
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console.log(specificity.b); // 1 |
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console.log(specificity.c); // 0 |
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``` |
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_`selectorSpecificity` takes a single selector, not a list of selectors (not : `a, b, c`). |
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To compare or otherwise manipulate lists of selectors you need to call `selectorSpecificity` on each part._ |
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### Comparing |
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The package exports a utility function to compare two specificities. |
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```js |
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import { selectorSpecificity, compare } from '@csstools/selector-specificity'; |
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const s1 = selectorSpecificity(ast1); |
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const s2 = selectorSpecificity(ast2); |
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compare(s1, s2); // -1 | 0 | 1 |
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``` |
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- if `s1 < s2` then `compare(s1, s2)` returns a negative number (`< 0`) |
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- if `s1 > s2` then `compare(s1, s2)` returns a positive number (`> 0`) |
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- if `s1 === s2` then `compare(s1, s2)` returns zero (`=== 0`) |
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## Prior Art |
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- [keeganstreet/specificity](https://github.com/keeganstreet/specificity) |
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- [bramus/specificity](https://github.com/bramus/specificity) |
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For CSSTools we always use `postcss-selector-parser` and want to calculate specificity from this AST. |
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[cli-url]: https://github.com/csstools/postcss-plugins/actions/workflows/test.yml?query=workflow/test |
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[discord]: https://discord.gg/bUadyRwkJS |
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[npm-url]: https://www.npmjs.com/package/@csstools/selector-specificity |
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[Selector Specificity]: https://github.com/csstools/postcss-plugins/tree/main/packages/selector-specificity
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