Javascript vendor libraries via CDN with local fallback

file.html

<!-- JQUERY -->
<script src="//cdnjs.cloudflare.com/ajax/libs/jquery/2.0.3/jquery.min.js"></script>
<script>window.jQuery || document.write('<script src="/js/vendor/jquery-2.0.3.min.js"><\x3C/script>')</script>

<!-- JQUERY UI -->
<script src="//cdnjs.cloudflare.com/ajax/libs/jqueryui/1.10.3/jquery-ui.min.js"></script>
<script>window.jQuery.ui || document.write('<script src="/js/vendor/jquery.ui-1.10.3.min.js"><\x3C/script>')</script>

<!-- JQUERY VALIDATE -->
<script src="//cdnjs.cloudflare.com/ajax/libs/jquery-validate/1.11.1/jquery.validate.min.js"></script>
<script>window.jQuery.validator || document.write('<script src="/js/vendor/jquery.validate-1.11.1.min.js"><\x3C/script>')</script>

<!-- JQUERY COOKIE -->
<script src="//cdnjs.cloudflare.com/ajax/libs/jquery-cookie/1.3.1/jquery.cookie.min.js"></script>
<script>$.cookie || document.write('<script src="/js/vendor/jquery.cookie-1.3.1.min.js"><\x3C/script>')</script>

<!-- MODERNIZER -->
<script src="//cdnjs.cloudflare.com/ajax/libs/modernizr/2.6.2/modernizr.min.js"></script>
<script>window.Modernizr || document.write('<script src="/js/vendor/modernizr-2.6.2.min.js"><\x3C/script>')</script>

<!-- LESS CSS -->
<script src="//cdnjs.cloudflare.com/ajax/libs/less.js/1.4.1/less.min.js"></script>
<script>window.less || document.write('<script src="js/vendor/less-1.4.1.min.js"><\x3C/script>')</script>

<!-- SELECTIVIZR -->
<!--[if (gte IE 6)&(lte IE 8)]>
    <script src="//cdnjs.cloudflare.com/ajax/libs/selectivizr/1.0.2/selectivizr-min.js"></script>
    <noscript><link rel="stylesheet" href="css/msie.css" /></noscript>
<![endif]-->

<!-- TWITTER BOOTSTRAP -->
<script src="//cdnjs.cloudflare.com/ajax/libs/twitter-bootstrap/3.0.0/js/bootstrap.min.js"></script>
<script>$.fn.modal || document.write('<script src="/js/vendor/bootstrap-3.0.0.min.js"><\x3C/script>')</script>

<!-- CKEDITOR -->
<script src="//cdnjs.cloudflare.com/ajax/libs/ckeditor/4.2/ckeditor.js"></script>
<script>window.CKEDITOR || document.write('<script src="/js/vendor/ckeditor/ckeditor.js"><\x3C/script>')</script>

Because there really is no publicly facing functions to latch onto in either the additional methods or the localization methods, you wouldn't be able to call those scripts in this same manner.

That being said, this method of loading scripts from CDN individually is somewhat antiquated. It's far better to use a build tool (like Grunt) to pull in all vendor libraries and compile them into a single script file. Then, of course, you would want to host that script file on a CDN service like MaxCDN or Amazon S3. Not only would this reduce HTTP requests tremendously, but it would reduce overall filesize, reduce load time by having the resource on a cookie-less domain, but would also ensure that you are always incorporating the latest versions of these libraries into your project.