javascript Unable to get property value of undefined or null reference

Question

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    lt html lang  en  xml lang  en  xmlns  http   www w3 org 1999 xhtml  gt   lt head gt       lt title gt  lt  title gt       lt meta content  text html charset iso-8859-2  http-equiv  content-type    gt    lt script type  text javascript  gt   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      lt  script gt   lt  head gt   lt body  lt form method  post  action    name  frm new user request  id  frm new user request  onsubmit  return validate frm new user request     gt   lt center gt   lt table gt       lt tbody gt            lt tr align  left  gt               lt td gt  lt Label gt ISID lt em gt    lt  Label gt  lt input maxlength  15  id  u userid  name  u userid  size  20  type  text   gt  lt  td gt               lt td gt    lt tr gt               lt td align  center  colspan  4  gt                   lt input type  image  src  images button btn create request gif  border  0  ALT  Create New Request  gt                    lt  td gt           lt  tr gt       lt  table gt   lt  form gt   lt  body gt   lt  html gt

User · Answer

you have many HTML and java script mistakes includes: tag, using non UTF-8 encoding for form submission, no need,... You must use document.forms.FORMNAME or document.forms[0] for first appear form in page Corrected:

_x000D_

 function validate_frm_new_user_request()_x000D_
{_x000D_
    alert('test');_x000D_
    var valid = true;_x000D_
_x000D_
    if ( document.forms.frm_new_user_request.u_userid.value == "" )_x000D_
    {_x000D_
        alert ( "Please enter your valid ISID Information." );_x000D_
        document.forms.frm_new_user_request.u_userid.focus();_x000D_
        valid = false;_x000D_
  console.log("FALSE::Empty Value ");_x000D_
    }_x000D_
return valid;_x000D_
}

_x000D_

<html lang="en" xml:lang="en" xmlns="http://www.w3.org/1999/xhtml">_x000D_
<head>_x000D_
    <title></title>_x000D_
    <meta content="text/html;charset=UTF-8" http-equiv="content-type" />_x000D_
_x000D_
_x000D_
</head>_x000D_
<body>_x000D_
<form method="post" action="" name="frm_new_user_request" id="frm_new_user_request" onsubmit="return validate_frm_new_user_request();">_x000D_
<center>_x000D_
<table>_x000D_
_x000D_
        <tr align="left">_x000D_
            <td><Label>ISID<em>*:</Label><input maxlength="15" id="u_userid" name="u_userid" size="20" type="text"/></td>_x000D_
            </tr>_x000D_
_x000D_
<tr>_x000D_
            <td align="center" colspan="4">_x000D_
                <input type="image" src="btn.png" border="0" ALT="Create New Request">_x000D_
_x000D_
                </td>_x000D_
        </tr>_x000D_
    </table>_x000D_
</form>_x000D_
</body>_x000D_
</html>

_x000D_

User · Answer

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    input with ID  element   var value       element  value input with class  element   var value       element  value

User · Answer

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

[javascript] javascript Unable to get property 'value' of undefined or null reference

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