使用错误的onload（）吗？

enter image description here is this wrong because i get loadData as undefined?

 <head>
 <script type="text/javascript">               
  function loadData() {
    var name  = $("#surname").val();        
    $.ajax({     
      url: 'checkdata.php',                      
      type: 'POST',       
      data: { 'surname' : surname }        
    });
    alert(data);
   //return false;
 </script>
 </head>
<body onload="loadData()">
 <form name="form1" method="post" action="php/save-edit.php" >

i have a form where i want to extract data from a db and display it in the form fields on form load

This problem might be happened because of running the onload event before creating the HTML object.

It would be better if you use like as follow :

$( document ).ready(function() { your function });

Hope this help.

As per my understand you are using code code.Please try below code. Just change <body onload="loadData()"> to <body onload="javascript:loadData();"> and try. it may help.

<head>
 <script type="text/javascript">               
  function loadData() {
    var name  = $("#surname").val();        
    $.ajax({     
      url: 'checkdata.php',                      
      type: 'POST',       
      data: { 'surname' : name }        
    });
    alert(data);
   //return false;
 }
 </script>
 </head>
<body onload="javascript:loadData();">
 <form name="form1" method="post" action="php/save-edit.php" >