js 方法点击第一次进入一次点击第二次进入两次以此类推

   $('#centre li:has(ul)').children(':first-child').click( function(e){
    // element vars
    var el = $(this).parent().children('ul').first();
    var isOpen = $(this).parent().hasClass('mtree-open');
     alert(isOpen);
    console.log($(this).parent().html());
    // force auto height of element so actual height can be extracted 力汽车元素,所以实际高度的高度可以提取
    el.css({'height': 'auto'}); 
    // Velocity.js animate element Velocity.js 动画元素
     if($.Velocity) {
      el.velocity('stop').velocity({
      //  translateZ: 0, // optional hardware-acceleration is automatic on mobile  可选硬件加速的自动移动
        height: isOpen ? [0, el.outerHeight()] : [el.outerHeight(), 0] 
       },{
        queue: false,
        duration: duration,
         easing: easing,
         display: isOpen ? 'none' : 'block',
         begin: setNodeClass($(this).parent(), isOpen),
         complete: function(){
           if(!isOpen) $(this).css('height', 'auto');
         }
       });
    //jQuery fallback animate element jQuery后备动画元素
     } else {
      setNodeClass($(this).parent(), isOpen);
       el.slideToggle(duration);
     } 
    // We can't have nodes as links unfortunately  不幸的是我们不能有节点链接
    //e.preventDefault();
    });