How do I access the element ID in an asp.net masterpage with JavaScript?

Question

I know there are a few answers to this question.

Usually the answers given online involve doing this...

document.getElementById (<%=myElementID.ClientID %>);

rather than this...

document.getElementById("myElementID");

However, even when I do it the first way, my JavaScript code still cannot find the element. It tells me the element is undefined.

So...just for testing...I tried to strip out all my JavaScript code and access the element with an alert box like this...

<script type="text/javascript">
    alert(document.getElementById('<%=searchHyperLink.ClientID %>').value);
</script>

It still tells me its undefined.

But its not freaking undefined! When I view the page source, the id rendered by <%=searchHyperLink.ClientID %> exactly matches the id of the control I want to find.

Any suggestions?

Where did you put this alert? Is the DOM ready by that point? — Evan Trimboli
– Evan Trimboli, Commented Aug 10, 2011 at 22:58

Jacob · Accepted Answer · 2011-08-10 23:23:52Z

4

To expand on Evan's comment, if you're doing the document.getElementById in a script tag that's before the element in the ordering of the document, it will return undefined. Try this instead:

<html>
  <head>
    <script>
        function postLoadFn() {
            alert(document.getElementById('<%=searchHyperLink.ClientID %>').innerHTML);
        }
    </script>
  </head>
  <body onload="postLoadFn();">
    <!-- Your markup here -->
  </body>
</html>

answered Aug 10, 2011 at 23:23

Jacob

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Comments

Alejandro D.V. · Accepted Answer · 2019-04-05 18:00:38Z

0

I've used parent to access a higher level in my project asp.net masterpage(home.master).

Instead of:

document.getElementById (<%=myElementID.ClientID %>);

Use:

parent.window.document.getElementById (<%=myElementID.ClientID %>);

edited Apr 5, 2019 at 18:00

answered Apr 4, 2019 at 20:00

Alejandro D.V.

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