Firefox web browser - Errors in JS console (app.min.js file)


We are having issues with a lot of our training in the Firefox web browser. Sometimes, the training will refuse to start, displaying errors in the javascript console.

The errors come from the app.min.js file, which is a file supplied by Storyline 360. Being minified, it is impossible to diagnose what the exact problem is, or how we could begin to fix it.

When the training refuses to start, the console errors are as follows:
TypeError: n is null app.min.js:3:473050 <anonymous> https://<path to training>/html5/lib/scripts/app.min.js:3:473050
<anonymous> https://<path to training>/html5/lib/scripts/app.min.js:3:472937
<anonymous> https://<path to training>/html5/lib/scripts/app.min.js:3:471529

TypeError: t.fixers is undefined app.min.js:3:471126 fix https://<path to training>/html5/lib/scripts/app.min.js:3:471126
styleAttribute https://<path to training>/html5/lib/scripts/app.min.js:3:470782
forEach self-hosted:268:13
process https://<path to training>/html5/lib/scripts/app.min.js:3:470958

To help diagnose the issue, here is our setup:
- Our LMS is hosted in one domain, let's call it
- The training files are hosted in another domain, let's call it domain.two
- loads domain.two/player.html in an iframe
- domain.two/player.html loads the training contents in an iframe
- the SCORM javascript API is loaded by domain.two/player.html
- Being cross-domain, we have javascript from talking with javascript on domain.two/player.html via the window.postMessage() APIs

The same training content does not have any issues when everything is hosted on the same domain and player.html is loaded in a child window instead of an iframe. We have not tested other setups (all on the same domain with iframes, or two separate domains with a child window).

To be clear, our problem is not with our cross-domain setup. It works perfectly on IE11, Microsoft Edge, and Google Chrome. The issue is really that sometimes on Firefox, about 75% of the time, a training will refuse to start, giving us the aforementioned errors in the console. Refreshing sometimes works on Firefox.

Any idea what the problem could be in the javascript? This is preventing us from going to production with our new LMS solution.

Thank you for sharing your thoughts :-)

Tina Marie

1 Reply