css-inline-stream/css-ruleparser.js

Inline CSS classes into styles from HTML streams

const parseStyle = require("./parse-style");

module.exports = function parseCSSToMap(cssString) {
    // Remove comments and whitespace
    cssString = cssString
      .replace(/\/\*[\s\S]*?\*\//g, '') // Remove comments
      .replace(/\s+/g, ' ')             // Normalize whitespace
      .trim();
    
    // Regex to match selectors and their rulesets
    // Captures: Group 1 = selector, Group 2 = ruleset content
    const ruleRegex = /([^{]+)\{([^}]+)\}/g;
    
    // Create map to store results
    const cssMap = new Map();
    
    // Find all matches and add to map
    let match;
    while ((match = ruleRegex.exec(cssString)) !== null) {
      const selector = match[1].trim();
      const ruleset = parseStyle(match[2].trim());
      
      // If selector already exists, combine rulesets
      mergeSelectorRule(selector,ruleset,cssMap);
    }
    
    return cssMap;
  }

  module.exports.mergeSelectorRule = mergeSelectorRule;
  function mergeSelectorRule(selector,ruleset,cssMap) {
    if (cssMap.has(selector)) {
        const existingRules = cssMap.get(selector);
        
        cssMap.set(selector,{...existingRules, ...ruleset});
      } else {
        cssMap.set(selector, ruleset);
      }
  }