Getting all keywords and types from CSSTree lexer

getPropValues.js

const getPropValues = (prop) => {
  const keywords = [];
  const types = [];
  const searcher = (node) => {
    if (!node) return;
    if (node.type === 'Keyword' && keywords.indexOf(node.name) === -1) {
      keywords.push(node.name);
    } else if (node.type === 'Group') {
      node.terms.map(term => csstree.grammar.walk(term, { enter: searcher }));
    } else if (node.type === 'Type') {
      if (types.indexOf(node.name) === -1) {
        types.push(node.name);
        const typeSource = csstree.lexer.properties[node.name] || csstree.lexer.types[node.name];
        if (typeSource && typeSource.syntax) {
          csstree.grammar.walk(typeSource.syntax, { enter: searcher });
        }
      }
    }
  }
  
  csstree.grammar.walk(csstree.lexer.properties[prop].syntax, {
    enter: searcher
  });

  return {
    keywords: keywords,
    types: types
  };
};