text: /**
   * 回调队列类
   * 
   * @export
   * @class Queue
   */
  export default class Queue {
  
      /**
       * 回调队列
       * 
       * @type {Array<Function>}
       * @memberof Callback
       */
      list = [];
  
      /**
       * 添加回调
       * 
       * @param {Function} fn 
       * @memberof Callback
       */
      add(fn) {
          this.list.push(fn);
      }
  
      /**
       * 清空队列
       * 
       * @memberof Callback
       */
      clear() {
          this.list = [];
      }
  
      /**
       * 依次出列
       * 
       * @memberof Callback
       */
      dequeue() {
          while (this.list.length) {
              let item = this.list.shift();
              item();
          }
      }
  
  }
  