Why is my javascript function not found by the page it is embedded in?

Question

I have a page that has a simple javascript in the header portion of the page:

<script type="text/javascript">
    function doLogout() {
        var conf = confirm("Really log out?");
        if (conf === true) {      //changed == to === for boolean comparison
            $.post("logout.aspx");
        }
    }
</script>

It uses jQuery to do an AJAX post to my logout page. The only issue right now is that when I click on the link (<a href="#" onclick="doLogout();">logout</a>) to fire this function, nothing happens. I checked FireBug's console, and it told me that the function is not defined. This has happened to me before, but I think I botched a bunch of code to fix it sometimes.

Does anyone know the proper way to fix this issue?

Edit

After doing a lot of googling and trying different things, I found this very concise and informative post. Apparently, as the linked article states, the way the script is referenced in the web site is important as it won't run properly otherwise! Hopefully this information will be useful for more people.

Answer 1

This can also occur if there is a syntax error earlier in your javascript code. Often this will just be interpreted as the function not existing (nor any function AFTER the error). Check the code above this code (if there is any) and this code for syntax errors.

A way to tell if the cache error is it is to open Firebug and view the Script source. If the page was cached, you won't see your code. If it loaded but has syntax errors, the code will show, though it won't "find" it.

Answer 2

Things to test:

1) Can you call this function from something else? Like add a <script> at the bottom of the page to call it?

2) Does the page validate? Sometimes I get screwy javascript errors if there is some busted HTML like a missing </b>

3) I've been starting to wrap my javascript in <![CDATA[ ]]> just incase I've got goofy chars in my javascript.

4) I assume you've tested this in other browsers and have the same behavior, right?

5) If you haven't installed it already, install the Web Developer firefox addon. It has a nifty toolbar menu that will disable the cache for you so everything reloads.

6) As weird as it sounds, I once hit a javascript issue that was because of how my text editor was saving UTF-8 files. I forget the details, but it was adding some byte-order-mark or something that upset the browser.