Css-selector-extract NPM

css-selector-extract

With selector extracting, it is possible to extract certain CSS selectors (RegEx can be used to match selectors) from CSS code. This is especially useful if you want to extract only a few CSS classes from a huge library or framework.

Demos

const cssSelectorExtract = require('css-selector-extract');

const options = {
  // CSS source code as string.
  css: '.btn { } .btn-alert { } .btn-success { }',
  // Array of selectors which should get extracted.
  filters: ['.btn']
};

// Asynchronous:
cssSelectorExtract.process(options).then((extractedCss) => {
  console.log(extractedCss); // Outputs: `.btn { }`.
});

// Synchronous:
const extractedCss = cssSelectorExtract.processSync(options);
console.log(extractedCss); // Outputs: `.btn { }`.

Rename extracted selectors

const cssSelectorExtract = require('css-selector-extract');

const options = {
  // CSS source code as string.
  css: '.btn { } .btn-alert { } .btn-success { }',
  // Array of selector filter objects with selectors
  // which should get extracted and replaced.
  filters: [{ selector: '.btn', replacement: '.button' }]
};

// Asynchronous:
cssSelectorExtract.process(options).then((extractedCss) => {
  console.log(extractedCss); // Outputs: `.button { }`.
});

RegEx

Filter selectors

const cssSelectorExtract = require('css-selector-extract');

const options = {
  css: '.btn { } .btn-alert { }',
  filters: [/^\..+-alert/]
};

cssSelectorExtract.process(options).then((extractedCss) => {
  console.log(extractedCss); // Outputs: `.btn-alert { }`.
});

Replace selectors

const cssSelectorExtract = require('css-selector-extract');

const options = {
  css: '.btn { } .btn-alert { }',
  filters: [{ selector: /^\.btn(.*)/, replacement: '.button$1' }]
};

cssSelectorExtract.process(options).then((extractedCss) => {
  console.log(extractedCss); // Outputs: `.button { } .button-alert { }`.
});

Usage with syntaxes other than pure CSS

Install the corresponding postcss syntax plugin (e.g. postcss-scss or postcss-less).

const cssSelectorExtract = require('css-selector-extract');
const postcssScss = require('postcss-scss');

const options = {
  css: '.nested { .selector { } }',
  filters: ['.nested'],
  postcssSyntax: postcssScss
};

cssSelectorExtract.process(options).then((extractedCss) => {
  console.log(extractedCss);
});

Preserve lines

Usually css-selector-extract removes all nodes which do not match the given selectors. However under some circumstances it might be useful to preserve the original line numbers (e.g. to keep source map references intact).

const cssSelectorExtract = require('css-selector-extract');

const options = {
  css: '.multiple { } .selectors {}',
  filters: ['.some-selector'],
  preserveLines: true
};

cssSelectorExtract.process(options).then((extractedCss) => {
  // Outputs the extracted selector(s) with empty lines where
  // other selectors got removed to preserve line numbers.
  console.log(extractedCss);
});

ES2015 named exports

import { process, processSync } from 'css-selector-extract';

const options = {
  // CSS source code as string.
  css: '.btn { } .btn-alert { } .btn-success { }',
  // Array of selectors which should get extracted.
  filters: ['.btn']
};

// Asynchronous:
process(options).then((extractedCss) => {
  console.log(extractedCss); // Outputs: `.btn { }`.
});

// Synchronous:
const extractedCss = processSync(options);
console.log(extractedCss); // Outputs: `.btn { }`.

Upgrade from 2.x.x to 3.x.x

With version 3.0.0 css-selector-extract takes an object as it's only parameter.

const cssSelectorExtract = require('css-selector-extract');
const postcssScss = require('postcss-scss');

// New way:
const options = {
  css: '.btn { } .btn-alert { } .btn-success { }',
  filters: ['.btn'],
  postcssSyntax: postcssScss
};
cssSelectorExtract.process(options);
cssSelectorExtract.processSync(options);

// Old way:
const css = '.btn { } .btn-alert { } .btn-success { }';
const selectorFilters = ['.btn'];
cssSelectorExtract.process(css, selectorFilters, postcssScss);
cssSelectorExtract.processSync(css, selectorFilters, postcssScss);