On what basis are javascript files cached?

Question

On what basis does javascript files get cached? Say I load a file with the name 'm-script.js' from one site and on another website I use the same name 'm-script.js' but with different contents. Will the browser fetch the new one, or just look at the name and load it from the cache? The urls for both the m-script.js file are different (obviously).
Thanks.

I also found that the web server adds and [ETag](http://en.wikipedia.org/wiki/HTTP_ETag) which is part of HTTP which is also used for cache validation. — , May 31 '12 at 06:03

score 4 · Accepted Answer · answered May 30 '12 at 06:01

If the url is different the cached copy will not be used. A new request will be made and the new file will be downloaded.

There would be a huge security and usability issue with the browser if a Javascript file cached from one website was used on another.

score 2 · Answer 2 · edited May 23 '17 at 12:22

2

Browsers cache files by their full URI.

This thread( How to force browser to reload cached CSS/JS files? ) will help you to understand.

edited May 23 '17 at 12:22

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answered May 30 '12 at 06:01

Sanghyun Lee

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score 1 · Answer 3 · answered May 31 '12 at 06:10

Since nobody has mentioned it yet, there is a lot more involved in HTTP caching than just the URI. There are various headers that control the process, e.g. Cache-Control, Expires, ETag, Vary, and so on. Requesting a different URI is always guaranteed to fetch a new copy, but these headers give more control over how requests to the potentially-cached resource are issued (or not issued, or issued but receive back a 304 Not Modified, or...).

Here is a detailed document describing the process. You can also google things like "caching expires" or "caching etag" for some more specific resources.

On what basis are javascript files cached?

3 Answers3

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