function highlight(js) {
    return js
      .replace(/</g, '&lt;')
      .replace(/>/g, '&gt;')
      .replace(/\/\/(.*)/gm, '<span class="comment">//$1</span>')
      .replace(/('.*?')/gm, '<span class="string">$1</span>')
      .replace(/(\d+\.\d+)/gm, '<span class="number">$1</span>')
      .replace(/(\d+)/gm, '<span class="number">$1</span>')
      .replace(/\bnew *(\w+)/gm, '<span class="keyword">new</span> <span class="init">$1</span>')
      .replace(/\b(function|new|throw|return|var|if|else)\b/gm, '<span class="keyword">$1</span>')
  }
Highlight the given string of `js`.