js中text接收子界面传回的值

       function FindData()
         {      
             var result=showModalDialog('Index_DJSearch.aspx','subpage','dialogWidth:520px;dialogHeight:500px;center:yes;help:no;resizable:no;status:no');  //打开模态子窗体,并获取返回值
             document.getElementsByName("txtjh")[0].value = result;
             document.getElementById("Hidden1").value = result;
             var ifnull =document.getElementsByName("txtjh")[0].value;
             if(ifnull   +   "" == "undefined")
                 document.getElementsByName("txtjh")[0].value = "请选择";
         }