JavaScript判断用户名和密码不能为空的实现代码

<script language="javascript"><!--
function VF_form1(){ //v2.0
<!--start_of_saved_settings-->
<!--type,password,name,Password,required,true,errMsg,密码不能为空!-->
<!--type,text,name,User,required,true,errMsg,用户名不能为空!-->
<!--end_of_saved_settings-->
  var theform = document.form1;
 var errMsg = "";
 var setfocus = "";
 
 
 if (theform['password'].value == "") {
   errMsg = "密码不能为空!";
 setfocus = "['password']";
 }
  if (theform['username'].value == "") {
   errMsg = "用户名不能为空!";
 setfocus = "['username']";
 }
  if (errMsg != ""){
   alert(errMsg);
 eval_r("theform" + setfocus + ".focus()");
 }
 else {
 theform.submit();
 }
} //-->
</script>