Provide two versions of jQuery: one for old, one for new

[mrmartineau]

As you know jQuery v2x loses browser support for oldIE and is now about 10% smaller in filesize. We can reduce page weight to users with more modern browsers by providing a conditional comment that separates the two versions so that oldIE gets v1x and modern browsers get v2x.

<!--[if lte IE 8]>
    <script src="//ajax.googleapis.com/ajax/libs/jquery/1.10.1/jquery.min.js"></script>
    <script>window.jQuery || document.write('<script src="/js/libs/jquery.min.js"><\/script>')</script>
<![endif]-->
<!--[if gt IE 8]><!-->
    <script src="//ajax.googleapis.com/ajax/libs/jquery/2.0.2jquery.min.js"></script>
    <script>window.jQuery || document.write('<script src="/js/libs/jquery.2.min.js"><\/script>')</script>
<!--<![endif]-->

Also see this gist as an example or my blog post about it

[pierrepavlov]

Isn't there chance for errors if the two versions differ too much?
I mean, you would almost need to make the same thing for main.js (if that is where you're writing your scripts).

I haven't really read about how much the version will differ except for the old IE-support, so please correct me if I'm wrong!

[necolas]

Thanks, but since we can't rely on 2.x and 1.x to be identical, this isn't something I think we should include.

[FagnerMartinsBrack]

For reference: #1353 (comment)

[mrmartineau]

Thanks @FagnerMartinsBrack, I hadn't seen that. On reflection, I think @necolas is right to ignore this but I still think that it can be useful to some developers.