code: function (index, lazy) {
  			if (this.opt.useAnimation) {
  				var steps = this.items[index].querySelectorAll(lazy || '.step');
  				for (var element of Array.prototype.slice.call(steps)) {
  					triggerAnim(element);
  				}
  				function triggerAnim(element) {
  					var delay = element.getAttribute('data-delay') || 100;
  					var timer = setTimeout(function () {
  						// 将style属性去除即可播放动画
  						element.style.visibility = '';
  						element.style.animationName = '';
  						clearTimeout(timer);
  					}, delay);
  				}
  			}
  		}
docs: 自动触发动画