Missing .map resource? [duplicate]

Question

I've recently started having this problem with all my projects. When my index page loads which contains a reference to the jquery source file, my console logs this error: GET http://localhost:3000/js/lib/jquery-1.10.2.min.map 500 (Internal Server Error).

This doesn't affect my application at all, but it's really annoying to see whenever I open up the console. Does anyone know where this is coming from?

Edit: Note that I'm not explicitly referencing the .map file, I am just pointing to <script src="js/lib/jquery-1.10.2.min.js"></script>

Answer 1

jQuery recently started using source maps.

For example, let's look at the minified jQuery 2.0.3 file's first few lines.

/*! jQuery v2.0.3 | (c) 2005, 2013 jQuery Foundation, Inc. | jquery.org/license //@ sourceMappingURL=jquery.min.map */ 

Excerpt from Introduction to JavaScript Source Maps:

Have you ever found yourself wishing you could keep your client-side code readable and more importantly debuggable even after you've combined and minified it, without impacting performance? Well now you can through the magic of source maps.

Basically it's a way to map a combined/minified file back to an unbuilt state. When you build for production, along with minifying and combining your JavaScript files, you generate a source map which holds information about your original files. When you query a certain line and column number in your generated JavaScript you can do a lookup in the source map which returns the original location. Developer tools (currently WebKit nightly builds, Google Chrome, or Firefox 23+) can parse the source map automatically and make it appear as though you're running unminified and uncombined files.

^{emphasis mine}

It's incredibly useful, and will only download if the user opens dev tools.

Solution

Remove the source mapping line, or do nothing. It isn't really a problem.

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Side note: your server should return 404, not 500. It could point to a security problem if this happens in production.