I just had this issue. All I needed was to run a simple javascript to test something, but it just would not run. In the end I cut it down to just a simple console log, and still nothing happened:
console.log('hello world'); //Nothing in the console!
Alright, I would not be creating a blog post if I did not have an answer to this. The answer is kind of embarrassing but I hope it can save some time for someone else out there. The problem was that I had written the script in this way:
<script src="SomeScript.js" />
I had used a self closing tag! and not a beginning and closing tag. What really annoys me is that in chrome I do see the script being loaded. It's just that nothing happens. All I had to do was to change the above to the following:
<script src="SomeScript.js"></script>
You can read more on why this behaviour occurs on stack overflow where there is - as always - a question on this. After years of being a web developer you still find yourself making these mistakes, however with all the javascript bundling these days it is rare you have to include a script manually.
I hope this helps someone out there! Let me know in the comments if it did :)