从Google的CDN加载jQuery的正确方法，如果需要，可以使用回退到本地库

Posted 2021-02-25

Proper way of loading libs such as jQuery from Google's CDN. Place these javascripts at the bottom for fast page loading. To target different versions, you can be more specific if you want; eg. /1.4/ or even /1.4.4/.

(NOTE: you may either use http:// or https:// depending on your needs. Both will work.)

<!-- Load jQuery from Google's CDN -->
<script src="//ajax.googleapis.com/ajax/libs/jquery/1.4.2/jquery.js"></script>
<!-- Fall back to local lib if loading from Google's CDN fails -->
<script>!window.jQuery && document.write(unescape('%3Cscript src="js/libs/jquery-1.4.4.js"%3E%3C/script%3E'))</script>