I am trying to get the value of a text field in a VF page in Java Script. Below is my VF page.

<apex:page id="thepage" standardController="Opportunity" extensions="OpportunityExt">  
 <apex:form id="theform"> 

        <script type="text/javascript">
        function initialize(){ 
        alert('called' + document.getElementById("thePage:theform:atextId").value);

          <apex:outputPanel id="inputId">
          <apex:commandLink id="saveBtn" onclick="initialize();" value="Search"/>
          <apex:outputPanel id="outputId">
             <apex:outputLabel value="{!$objecttype.Opportunity.fields.IsClosed__c.label}"/> 
             <apex:actionRegion >
               <apex:inputField value="{!Opportunity.IsClosed__c}" id="closedcheckboxId"/> 
             <apex:outputLabel value="{!$objecttype.Opportunity.fields.OrderNumber__c.label}"/> 
             <apex:actionRegion >
               <apex:inputField value="{!Opportunity.OrderNumber__c}" id="atextId"/> 


When I click the link I get this error in the inspect window.

Cannot read property 'value' of null

I might be missing something here. I checked the path of the text field using inspect window and I saw:

<input id="thepage:theform:atextId" maxlength="8" name="thepage:theform:atextId" size="20" type="text" value="731645">

What am I missing here. Why do I get a null?

  • @AdrianLarson you got this one?
    – sfdcfox
    Commented Sep 26, 2017 at 23:08
  • Wasn't planning on it.
    – Adrian Larson
    Commented Sep 26, 2017 at 23:10

1 Answer 1


In this case, it was a simple typo: the ID value is cAsE-sEnSiTiVe.

    alert('called' + document.getElementById("thepage:theform:atextId").value);
                                       //        ^ This P was capitalized

Always make sure you're matching the case for your Id values.

As a more practical solution, consider using $Component:

    alert('called' + document.getElementById("{!$Component.thePage.theform.atextId}").value);

Using $Component will resolve the element Id correctly (in a case-insensitive manner) so you don't have to worry about it as much.

  • Gotcha! Appreciate it.
    – SfdcBat
    Commented Sep 26, 2017 at 23:24

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