如何从纯JavaScript中的元素中删除类？

// 获取元素
var element = document.getElementById('myElement');

// 删除类
element.classList.remove('active');

element.classList.remove('nonExistentClass'); // 不会报错，但也不会有任何效果

element.classList.add('active');
element.classList.add('active');
element.classList.remove('active'); // 只会删除一个 'active' 类

<!-- Polyfill for classList -->
<script>
if (!Element.prototype.matches) {
  Element.prototype.matches = Element.prototype.msMatchesSelector || 
                              Element.prototype.webkitMatchesSelector;
}

if (!Element.prototype.closest) {
  Element.prototype.closest = function(s) {
    var el = this;
    if (!document.documentElement.contains(el)) return null;
    do {
      if (el.matches(s)) return el;
      el = el.parentElement || el.parentNode;
    } while (el !== null && el.nodeType === 1); 
    return null;
  };
}

if (!Element.prototype.classList) {
  Element.prototype.classList = {
    add: function(className) {
      this.className += ' ' + className;
    },
    remove: function(className) {
      this.className = this.className.replace(new RegExp('(^|\\b)' + className.split(' ').join('|') + '(\\b|$)', 'gi'), ' ');
    },
    contains: function(className) {
      return new RegExp('(^| )' + className + '( |$)', 'gi').test(this.className);
    }
  };
}
</script>