I've got several JavaScript files that load along with many of my pages, costing valuable tens of kilobytes of data download. One of these is a version of jquery.min.js which although minified, is still 25kb or so.
My issue is that a huge chunk of mobile phones don't support JavaScript so the downloading of this and other JS files is a waste of data. Is there anyway to lazy load the JQuery file by adding a <script> tag in the page that calls the JS file and would obviously only execute if a browser supports JavaScript, which would only then make sense to download it?
To load script files only under certain conditions, I have used something like:
ReplyDelete<script type="text/javascript">
document.write('<scr'+'ipt type="text/javascript" src="/js/jquery.min.js"></scr'+'ipt>');
</script>
Note: this only works inline, after the document is done loading, document.write() will have undesired effects.
Note 2: It is important to break '</script>' like '</scr'+'ipt>' so as to not confuse the browser's parser into thinking your true script block is ended. I do the opening script tag the same way for good measure.
function loadScript(filename) {
ReplyDeletevar t = document.createElement('script'),
s = document.getElementsByTagName('body')[0];
t.type = 'text/javascript';
t.async = true;
t.src = filename;
s.parentNode.appendChild(t);
}
// If and when jQuery is needed, you'd load it with:
loadScript('http://code.jquery.com/jquery.min.js');