jQuery的缓存机制浅析

 return cacheData[key];
}; 

  return cacheData[key];
 }
 else if( typeof key === "object" ){
  var index,
   thisCache;

  if( !key[expando] ){
   // 添加一个DOM元素的属性
   // 随机数是属性名 索引值是属性值
   index = key[expando] = uuid;
   thisCache = cacheData[index] = {};
  }
  else{
   index = key[expando];
   thisCache = cacheData[index];
  }

  
  if( !thisCache[expando] ){
   thisCache[expando] = {};
  }

  if( gambling data !== undefined ){
   // 将数据存到缓存对象中
   thisCache[expando][val] = data;
  }

  // 返回DOM元素存储的数据
  return thisCache[expando][val];
 }
};

var removeData = function( key, val ){
 if( typeof key === "string" ){
  delete cacheData[key];
 }
 else if( typeof key === "object" ){
  if( !key[expando] ){
   return;
  }
  // 检测对象是否为空
  var isEmptyObject = function( obj ) {
    var name;
    for ( name in obj ) {
     return false;
    }
    return true;
   },

   removeAttr = function(){
    try{
     // IE8及标准浏览器可以直接使用delete来删除属性
     delete key[expando];
    }
    catch (e) {
     // IE6/IE7使用removeAttribute方法来删除属性
     key.removeAttribute(expando);
    }
   },

   index = key[expando];

  if( val ){
   // 只删除指定的数据
   delete cacheData[index][expando][val];
   // 如果是空对象 索性全部删除
   if( isEmptyObject( cacheData[index][expando] ) ){
    delete cacheData[index];
    removeAttr();
   }
  }
  else{
   // 删除DOM元素存到缓存中的所有数据
   delete cacheData[index];
   removeAttr();
  }
 }
};

data( box, "myBlog", "stylechen.com" );
alert( data( box, "myBlog" ) ); // stylechen.com

removeData( box, "myBlog" );

alert( data( box, "myBlog" ) ); // undefined
alert( data( box, "myName" ) ); // chen
alert( box[expando] ); // 1

removeData( box );
alert( box[expando] ); // undefined