JavaScript not executing inside xul file

I am having trouble writing js in a XUL file. I have written a simple method inside xul but it doesn't execute when you open the browser.

This is the method inside the xul tag:

function demo() {
    alert('hello');
}

I ve tried to change the tag of the script from <script> to <html:script> but still method doesn't work. I tried开发者_C百科 to use methods from external js file using <html:script type="application/x-javascript" src="overlay.js"> still not working.

The name of the xul file is ff-sidebar.xul. Basically what I am trying to do is display text on the sidebar using javascript functions that are in external js files. I really need javascript to work inside xul file so I can use the js methods. I know for sure that nothing is wrong with the js file.

I think you have an addressing problem in your JavaScript reference. I believe Firefox is not able to locate overlay.js. Try this:

<script type="application/javascript" src="chrome://sidebar/content/overlay.js">

where "sidebar" is the name of your app, and your .js file is located in the "sidebar/chrome/content" directory, alongside your sidebar.xul file.

More information on the chrome URL can be found here.