JavasScript function undefined

Question

JavasScript function undefined

2.1k Views Asked by user2216177 At 16 April 2025 at 16:01

i've got an html element declared as so:

<div id="taskImage" runat="server">
   <a href="javascript:void(0);" onclick="switchViews('div<%# Eval("proId") %>', 'one');">
      <img id='imgdiv<%# Eval("proId") %>' alt="Click to show/hide tasks" border="0" src="..."/>
   </a>
</div>

and the javascript function switchViews is declared post-html as such:

function switchViews(obj, row) {

      var div = document.getElementById(obj);
    var img = document.getElementById('img' + obj);

    if (div.style.display == "none") {
        div.style.display = "inline";

        img.src = "../../images/icons/delete.png";

    }
    else {
        div.style.display = "none";

        img.src = "../../images/icons/add.png";

    }

}

when I click on the html element, i get thrown a JS error saying "Object Exepcted", and in the google chrome script debugger it says that switchViews is undefined. Why would it think that switchViews is undefined and how would I go about fixing it? For the record I have tried it with the javascript declared before the html and with the switchViews call in the href attribute but it all ends the same.

EDIT : to clear something up, by post-html and pre-html i mean before and after i write out the html elements. so post would be like

<div>
   <!-- All my html stuff -->
<div>
<script type="text/javascript">
   <!-- All my Javascript -->
</script>

and pre would be the reverse of that

Original Q&A

There are 2 best solutions below

Jeffrey Blake On 19 April 2013 at 20:43

Your javascript should not be declared outside of the HTML tags. It needs to be declared inside a <script>...</script> block, and that block should be placed inside the <html>...</html> block, typically inside the <head>

So the overall structure should be something like:

<html>
  <head>
    <script>
       //your JavaScript goes here
    </script>
  </head>
  ...
</html>

There are other variations that are valid too, but they will all require everything to be inside the overall <html> tag.

If that is satisfied, then you are almost certainly running into an issue with either having an error in your javascript code (if the browser can't parse the function, then it stays undefined) or you have a naming conflict (if you have multiple functions set to the same name or if your function has the same name as an id of one of your html elements, then it will often result in an undefined error).

You will have to check for naming conflicts yourself, but you can confirm whether or not it is a javascript error by commenting out all of your code and replacing it with something like: alert("this works");

You could then add your code back in one line at a time until the alert fails to fire (making sure to always have matching parens/brackets, of course). When it fails, you will have found the error.

**Paul S.** · Accepted Answer

Question

At the point where <a href="javascript:void(0);" onclick="switchViews(... etc is encountered by the browser, does the function switchViews exist or is it undefined?

Answer

The code defining switchViews appears after, so at that time switchViews is undefined.

Solution

Place your <script> before the rest of the HTML or attach the event listener in your JavaScript instead of inline. This can be done via addEventListener or using jQuery and may require you to loop over your HTMLElements of interest.

JavasScript function undefined

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