GC与JS内存泄露（5）

三、Cross-Page-Leaks

仍然先看一个例子：

< html >
     < head >
         < script language = “ JScript “ > function  LeakMemory()  
        {
             var  hostElement  =  document.getElementById( “ hostElement “ ); //  Do it a lot, look at Task Manager for memory response
             for (i  =   0 ; i  <   5000 ; i ++ )
            {
                 var  parentDiv  =
                    document.createElement( “ <div onClick=’foo()’> “ );
                 var  childDiv  =
                    document.createElement( “ <div onClick=’foo()’> “ ); //  This will leak a temporary object
                parentDiv.appendChild(childDiv);
                hostElement.appendChild(parentDiv);
                hostElement.removeChild(parentDiv);
                parentDiv.removeChild(childDiv);
                parentDiv  =   null ;
                childDiv  =   null ;
            }
            hostElement  =   null ;
        } function  CleanMemory()  
        {
             var  hostElement  =  document.getElementById( “ hostElement “ ); //  Do it a lot, look at Task Manager for memory response
             for (i  =   0 ; i  <   5000 ; i ++ )
            {
                 var  parentDiv  =   document.createElement( “ <div onClick=’foo()’> “ );
                 var  childDiv  =   document.createElement( “ <div onClick=’foo()’> “ ); //  Changing the order is important, this won’t leak
                hostElement.appendChild(parentDiv);
                parentDiv.appendChild(childDiv);
                hostElement.removeChild(parentDiv);
                parentDiv.removeChild(childDiv);
                parentDiv  =   null ;
                childDiv  =   null ;
            }
            hostElement  =   null ;
        }
         </ script >
     </ head > < body >
         < button onclick = “ LeakMemory() “ > Memory Leaking Insert </ button >
         < button onclick = “ CleanMemory() “ > Clean Insert </ button >
         < div id = “ hostElement “ ></ div >
     </ body >
</ html >

LeakMemory和CleanMemory这两段函数的唯一区别就在于他们的代码的循序，从代码上看，两段代码的逻辑都没有错。