var val = "stylechen.com";
$("div").data( "url" ); // 返回undefined
$("div").data( "url", val ); // 返回"stylechen.com"
$("div").data( "url" ); // 返回"stylechen.com"

var cacheData = {}; // 用來存儲數據的全局對象
var data = function( key, val ){
 if( val !== undefined ){
  cacheData[key] = val;
 }

 return cacheData[key];
}; 

var cacheData = {}, // 用來存儲數據的全局對象
 uuid = 0,
 // 聲明隨機數
 expando = "cacheData" ( new Date() "" ).slice( -8 );

var data = function( key, val, data ){
 if( typeof key === "string" ){
  if( val !== undefined ){
   cacheData[key] = val;
  }

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

  if( !key[expando] ){
   // 添加一個DOM元素的屬性
   // 隨機數是屬性名 索引值是屬性值
   index = key[expando] = uuid;
   thisCache = cacheData[index] = {};
  }
  else{
   index = key[expando];
   thisCache = cacheData[index];
  }

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

  if( <a >gambling</a> data !== undefined ){
   // 將數據存到緩存對象中
   thisCache[expando][val] = data;
  }

  // 返回DOM元素存儲的數據
  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;
  }
  // 檢測對象是否為空
  var isEmptyObject = function( obj ) {
    var name;
    for ( name in obj ) {
     return false;
    }
    return true;
   },

   removeAttr = function(){
    try{
     // IE8及標準瀏覽器可以直接使用delete來刪除屬性
     delete key[expando];
    }
    catch (e) {
     // IE6/IE7使用removeAttribute方法來刪除屬性
     key.removeAttribute(expando);
    }
   },

   index = key[expando];

  if( val ){
   // 只刪除指定的數據
   delete cacheData[index][expando][val];
   // 如果是空對象 索性全部刪除
   if( isEmptyObject( cacheData[index][expando] ) ){
    delete cacheData[index];
    removeAttr();
   }
  }
  else{
   // 刪除DOM元素存到緩存中的所有數據
   delete cacheData[index];
   removeAttr();
  }
 }
};

var box = document.getElementById( "box" ),
 list = document.getElementById( "list" );

data( box, "myName", "chen" );
alert( data( box, "myName" ) ); // chen

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