css-prefix-loader.js

import { getOptions } from 'loader-utils';
import CSS from 'css';
import XRegExp from 'xregexp';


export default function cssPrefixLoader(content) {
    const { prefix, ...options } = getOptions(this);

    let ast = CSS.parse(content);

    addPrefixes(prefix, ast.stylesheet.rules);

    return CSS.stringify(ast, options);
}


const selectorRx = XRegExp('(?<=[.#])([a-zA-Z0-9_-]+)', 'g');

function addPrefixes(prefix, rules) {
    for (let rule of rules) {
        if (rule.selectors) {
            rule.selectors = rule.selectors.map(selector =>
                selector.replace(selectorRx, prefix + '$1')
            );
        }
        if (rule.rules) {
            addPrefixes(prefix, rule.rules);
        }
    }
}