How to load local files if CDN is not working

I am using some CDN js and css files.

I searched in Google that how to load local data if CDN is not working.

i found a good link written like this

<script class="jsbin" src="http://ajax.googleapis.com/ajax/libs/jquery/1/jquery.min.js"></script>
        <script type="text/javascript">
            if (typeof jQuery == 'undefined') {
                document.write(unescape("%3Cscript src='JS/Plugins/jquery-1.8.2.min.js' type='text/javascript'%3E%3C/script%3E"));
            }
        </script>

Yes its working but then i tried for another CDN network ,then its not downloading from local. if the CDN is not working then it is showing error in my page and the page is not working properly due to that missing that js file. means :

<script type="text/javascript" src="http://code.jquery.com/ui/1.9.1/jquery-ui.js"></script>
<script type="text/javascript">
    if (typeof jQuery == 'undefined') {
        document.write(unescape("%3Cscript src='Include/JS/JqueryPlugin/jquery.min.js' type='text/javascript'%3E%3C/script%3E"));
    }
</script>

in the above case the local jquery.min.js is not downloading when the above CDN is not working .

similarly how to do for CSS(searched in Google and not found any good solution).

How to do know which CDN is not working and download respective files from local.

Please help

Thanks in advance