jQuery Linking vs. Download?

Which way is better? To link to the jQuery Pack at http://ajax.googleapis.com. Or to download the appropriate file and link locally? Does it matter? Is there a chance the link may disappear? Or is there a chance the file online will be updated开发者_运维知识库, and it's better to link to it? Curious.

Thanks, Tracy

From the Google Code site:

Google works directly with the key stake holders for each library effort and accepts the latest stable versions as they are released. Once we host a release of a given library, we are committed to hosting that release indefinitely.

One of the main points of Google hosting the jQuery library is so that it is cached in a single place. Consider the following scenario:

1. User visits site A
2. Site A has jQuery on the same domain, so the file is downloaded by the browser
3. User visits site B
4. Site B has jQuery on the same domain, so the file is downloaded by the browser a second time.

Now if we all fetched jQuery from the Google servers, the scenario goes like this:

1. User visits site A
2. Site A loads jQuery from Google, so it's downloaded by the browser
3. User visits site B
4. Site B loads jQuery from Google, but the browser already downloaded it and cached it, so fetching the file again is instantaneous.

What if the user comes from a country where Google is banned? Also, some time ago we had to pay for international internet traffic (while regional traffic was "free") in my country an I suspect it may be still the case in some other countries. Users would be upset for having to pay for jQuery. Even minimized. It's safer to keep the files you need on your server.

EDIT: Another reason for not using jQuery from Google servers (if used on your intranet: https://meta.stackexchange.com/questions/10071/employer-blocks-jquery-from-google-doh)

I think linking to Google's edge cache servers usually makes sense. Google is almost certainly going to have better up time than you and they are likely to be at least as responsive. Plus, there's the advantage that an incoming user has already cached jQuery from them so they don't have to download it at all.

The only situation I can think of where I wouldn't do this would be for a site that was primarily used as in intranet, wherein the local copy would truly be local to most visitors (e.g. on the lan).

One important argument for linking to the file on google is that the user might already have the file in his cache, if he's been on another site recently that uses the same url.

YOU decide, you control your file or not. One small factor is the bandwidth, but if you have a busy site where that REALLY matters, you will have the bandwidth anyway. What if some small change breaks your site and you have not yet tested with the newer version?

Id reccomend downloading it and storing jquery.js locally on the same server. That way if the linked to file goes down (not that google ever do).

A big argument is that if jquery release an update that removes a function that you need you wont be shafted over and you'll have time to fix it