You can study the HTML document that 'includes' the external JavaScript file. The JS file is often called foo.js or something close to that.

When you have the full URL of the .js file, some/many/all(?) http servers will let you surf the .js file as if it was an html document. As a result, you will see the full .js file in the browser.

Disclaimer: I have tried this on a few servers and it was a while ago. But the technique should probably work in most cases.

OTOH, I don't think this was what the original poster wanted to achieve.

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Everything went worng, just as foreseen.