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>