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layout: docpage
title: Debug the application
---

# Debug the application

If the application built and showed a set of columns but no commit data, then you are probably running a browser that has a tighter security model than some other browsers.  Some browsers won't let an application access data from another domain without permission.

But to verify that, or whenever something goes wrong in your application, the first step is to open the console window for your browser.  How to do that depends on the browser, but basically, the output JavaScript is going to be executed until it throws an "uncaught exception" and code that was supposed to run after that won't and that will result in lots of things not working.

In one browser, the console said:

```
Failed to load file:///.../bin/js-debug/project.json: Cross origin requests are only
        supported for protocol schemes: http, data, chrome, chrome-extension, https.
```

Because I had simply opened the file from my computer's file viewer in the browser, the browser opened it under the file:/// protocol and wouldn't allow access from my computer to GitHub.

So, to do further testing you will need to set up a web server for the application or copy the application to a web server and run it from there.  If you look in the "js-debug" folder, you will find a lot of files you have to copy. You can't just copy the index.html file.

Back to the topic of debugging for a moment. Most browsers also have debuggers with breakpoints. Your application .mxml and .as files have each been turned into a .js file that the browser will let you set breakpoints in and step through. Some IDEs support the ability to see your .mxml and .as files in the debugger.

Anyway, to get this application to access GitHub, we have to make the application available on a web server and learn a bit about security.

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