使用外部托管脚本和本地托管脚本之间有速度差异吗？

Question

I've been using the jQuery library hosted by Google on my site. Will it load quicker if I host it locally?

Answer 1

Here are a few factors to think about:

1. Cache. If you are using the Google hosted jQuery, and another website is using the same version of jQuery hosted with Google, it will be cached locally already. Many ISPs will also cache this file for faster delivery to their customers as well.

2. Parallel downloading. Because jQuery will be downloaded from another domain, your maximum connection limit per domain (usually 4 per browser) won't have to queue jQuery.

3. Multiple locations. Google has servers all over the world, which results in faster downloads for international users.

Now that said, it is possible that your servers could be lightning fast with multiple locations, and setup for parallel downloading across different subdomains. Probably a bigger performance factor is the load priority that will be determined by load order of CSS and Javascript: http://code.google.com/speed/page-speed/docs/rtt.html#PutStylesBeforeScripts

Hope that helps!

Answer 2

Google has a CDN that stretches all over the world. In addition, most people have probably visited Google or one of its properties at some point before visiting your site-- which means they would already have Google's copy of jQuery cached.

If you're thinking of serving a copy of jQuery off your single server or cluster, Google will certainly beat you (and reduce your bandwidth usage). But if you have a CDN in place from Akamai or similar, you may find it better to serve your own minified copy.

Answer 3

Maybe, probably not. Google has a lot of DNS real-estate to minimize long-distance downloads, and there is a chance if you are using a common CDN URL that the user will already have the jquery file cached from visiting another site who used the same external link, and that would eliminate the download completely. That's the primary benefit of the CDN. Google is wicked slower than Akamai though, so if you're looking for sheer speed, Akamai is the way to go.

That being said, the URL you choose will make a difference. The major version URL has a short-expires header so it won't stay cached for nearly as long as a minor version URL. The minor version URL, though, will drastically reduce the odds that the user visited a site using the same exact minor version. Your odds are best by using the latest stable minor version CDN URL.

Answer 4

是的，它将快速加载，但是最好与google cdn一起使用，因为它将被google缓存，并且从长远来看会更快。