//一般是传的node,'script'
 //应该是用来获取context上的tag标签，或者是将context和context里的tag标签的元素合并
 //源码4893行
 function getAll( context, tag ) {
  // Support: IE <=9 - 11 only
  // Use typeof to avoid zero-argument method invocation on host objects (#15151)
  var ret;
  console.log(context,typeof context.getElementsByTagName,typeof context.querySelectorAll,'context4894')
  //如果context存在getElementsByTagName的方法的话
  if ( typeof context.getElementsByTagName !== "undefined" ) {
   //tag:script
   //从context中获取script标签的节点
   ret = context.getElementsByTagName( tag || "*" )
   console.log(tag,ret,'ret4897')
  }
 //DocumentFragment没有getElementsByTagName方法，但有querySelectorAll方法
 else if ( typeof context.querySelectorAll !== "undefined" ) {
   ret = context.querySelectorAll( tag || "*" );
  } else {
   ret = [];
  }
  console.log(nodeName( context, tag ),'nodeName4909')
  //nodeName() 判断两个参数的nodename是否相等
  if ( tag === undefined || tag && nodeName( context, tag ) ) {

   return jQuery.merge( [ context ], ret );
  }
  return ret;
 }

 // Support: Android <=4.0 only, PhantomJS 1 only
  // push.apply(_, arraylike) throws on ancient WebKit
  //源码461行
  //将second合并到first后面
  merge: function( first, second ) {
   var len = +second.length,
    j = 0,
    i = first.length;
   //依次将second的item添加到first后面
   for ( ; j < len; j++ ) {
    first[ i++ ] = second[ j ];
   }
   //first可能是类数组，所以需要更新下length属性
   first.length = i;
   return first;
  },

 //清除elems上的数据和事件
  //源码6146行
  cleanData: function( elems ) {
   var data, elem, type,
    //beforeunload/blur/click/focus/focusin/focusout/
    //load/mouseenter/mouseleave/pointerenter/pointerleave
    special = jQuery.event.special,
    i = 0;
   for ( ; ( elem = elems[ i ] ) !== undefined; i++ ) {
    //允许的节点类型
    if ( acceptData( elem ) ) {
     //当有事件绑定到elem后，jQuery会给elem一个属性dataPriv.expando
     //该属性上面就绑定了事件和数据
     if ( ( data = elem[ dataPriv.expando ] ) ) {
      //如果data上有事件的话
      if ( data.events ) {
       //逐个列举data上的事件，比如click
       for ( type in data.events ) {
        // 如果special中有data.events上的事件
        if ( special[ type ] ) {
         //调用jQuery.event.remove方法，移除elem上的event类型
         jQuery.event.remove( elem, type );
         // This is a shortcut to avoid jQuery.event.remove's overhead
        }
        //应该是自定义的事件
        else {
         //本质即elem.removeEventListener(type,handle)
         jQuery.removeEvent( elem, type, data.handle );
        }
       }
      }
      // Support: Chrome <=35 - 45+
      // Assign undefined instead of using delete, see Data#remove
      //最后将元素的dataPriv.expando属性置为undefined
      elem[ dataPriv.expando ] = undefined;
     }
     //dataUser应该是用户绑定的事件
     if ( elem[ dataUser.expando ] ) {
      // 将元素的dataUser.expando属性置为undefined
      // Support: Chrome <=35 - 45+
      // Assign undefined instead of using delete, see Data#remove
      elem[ dataUser.expando ] = undefined;
     }
    }
   }
  }

 //判断是否是指定的节点类型
 //只接受元素节点1，文档节点9，任意对象
 //返回true/false
 //源码4178行
 var acceptData = function( owner ) {
  // Accepts only:
  // - Node
  //  - Node.ELEMENT_NODE
  //  - Node.DOCUMENT_NODE
  // - Object
  //  - Any
  return owner.nodeType === 1 || owner.nodeType === 9 || !( +owner.nodeType );
 }

 //移除elem上的自定义监听事件
 //源码5599行
 //jQuery.removeEvent(elem,type,data.handle)
 jQuery.removeEvent = function( elem, type, handle ) {
  // This "if" is needed for plain objects
  if ( elem.removeEventListener ) {
   elem.removeEventListener( type, handle );
  }
 }