Add custom event listener to button

[Diggo11]

I'm trying to inject javascript onto the forum home page that will allow me to run a custom function when the button is pressed collapse/uncollapse a forum category: ()

PHP Code:

$template_hook['headinclude_bottom_css'] .= '<script type="text/javascript">' . "\n";  

$template_hook['headinclude_bottom_css'] .= "function toggleCollapsedPlugin(sender, collapseState) { 
    /* Do something */
} 

function initCollapsedPlugin() { 
    var forumcats = document.getElementById('forums').getElementsByTagName('li'); 
    var callCollapsedPlugin; 
    for (var i = 0; i < forumcats.length; i++) { 
        if (forumcats[i].className.indexOf('forumbit') >= 0 && forumcats[i].className.indexOf('L1') >= 0) { 
            var button = forumcats[i].getElementsByTagName('a')[1].getElementsByTagName('img')[0]; 
            if (button.src.indexOf('_collapsed') >= 0) { 
                toggleCollapsedPlugin(button, true); 
            } 
            callCollapsedPlugin = function(){ toggleCollapsedPlugin(button); }; 
            button.addEventListener('click', callCollapsedPlugin, false); 
        } 
    } 
}";  

$template_hook['headinclude_bottom_css'] .= '</script>' . "\n"; 


When I pause script execution using Chrome DevTools, I can step through the javascript and see the event listener supposedly being added. However, when I then click on any of the elements that were assigned to the button variable, the function toggleCollapsedPlugin is never called. Any ideas why?

--------------- Added [DATE]1342101636[/DATE] at [TIME]1342101636[/TIME] ---------------

http://stackoverflow.com/questions/1...bject-in-array