call javascript and then run php

Techissue2008

When I submit the button, it skips the javascript and directly calls login.php.

How can it check the js and then run php?

Thanks

Techissue2008

I changed the document.all to document.form and onsubmit event still not work

ichampin

<title>Untitled Document</title>
<script>
function checklogin()
{
var f = document.loginform;
if((f.pusername.value=="")||(f.pusername.value.length<4))
{
alert('wrong username');
f.pusername.focus();
return false;
}
if((f.ppassword.value=="")||(f.ppassword.value.length<4))
{
window.alert('wrong password');
f.ppassword.focus();
return false;
}
}
</script>
<FORM name="loginform" action="login.php" method="post">
<input name="pusername" type="text" style="width:135;height:22">
<input name="ppassword" type="password" style="width:135;height:22">
<input type="submit" name="login" id="login" value="" onClick="return checklogin();">
</form>
</head>

you have to write the name of the form in document.'form' and "isEmpty" I think is not a function in javascript, isEmpty doesn't work for me

Techissue2008

Your advice fix my problem, thank you so much.

if((ft.pusername.value=="")||(ft.pusername.value.length<4))
{
	window.alert('wrong username');
	ft.pusername.focus();
	return false;
}

and I use onSubmit in form tag.