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I have below code and java script is throwing error "Unable to get property 'value' of undefined or null reference". What am I doing wrong ? below is the sample code I am trying to execute to validate one input field.
<html lang="en" xml:lang="en" xmlns="http://www.w3.org/1999/xhtml">
<head>
<title></title>
<meta content="text/html;charset=iso-8859-2" http-equiv="content-type" />
<script type="text/javascript">
function validate_frm_new_user_request()
{
alert('test');
valid = true;
if ( document.frm_new_user_request.u_isid.value == '' )
{
alert ( "Please enter your valid ISID Information." );
document.frm_new_user_request.u_isid.focus();
valid = false;
}
return valid;
</script>
</head>
<body
<form method="post" action="" name='frm_new_user_request' id="frm_new_user_request" onsubmit="return validate_frm_new_user_request();">
<center>
<table>
<tbody>
<tr align="left">
<td><Label>ISID<em>*:</Label><input maxlength="15" id="u_userid" name="u_userid" size="20" type="text"/></td>
<td>
<tr>
<td align="center" colspan="4">
<input type="image" src="images/button/btn_create_request.gif" border="0" ALT="Create New Request">
</td>
</tr>
</table>
</form>
</body>
</html>
437
The issue is how you're attempting to get the value. Things like...
if ( document.frm_new_user_request.u_isid.value == '' )
won't work. You need to find the element you want to get the value of first. It's not quite like a server side language where you can type in an object's reference name and a period to get or assign values.
document.getElementById('[id goes here]').value;
will work. Note: JavaScript is case-sensitive
I would recommend using:
var variablename = document.getElementById('[id goes here]');
or
var variablename = document.getElementById('[id goes here]').value;
You can't access element like you did (document.frm_new_user_request). You have to use the function getElementById:
document.getElementById("frm_new_user_request")
So getting a value from an input could look like this:
var value = document.getElementById("frm_new_user_request").value
Also you can use some JavaScript framework, e.g. jQuery, which simplifies operations with DOM (Document Object Model) and also hides differences between various browsers from you.
Getting a value from an input using jQuery would look like this:
var value = $("#element).value
var value = $(".element).value
21
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