text: if (el.classList) {
      el.classList.toggle(className)
  } else {
      var classes = el.className.split(' ')
      var existingIndex = -1
      for (var i=classes.length; i--;){
        if (classes[i] === className)
          existingIndex = i;
      }
  
      if (existingIndex >= 0)
        classes.splice(existingIndex, 1)
      else
        classes.push(className);
  
      el.className = classes.join(' ')
  }
  