Load a script file asynchronously
How to load a JavaScript file asynchronously from the server and automatically execute it.
Loading an external script asynchronously is simple. Create a script tag, set its src
attribute, and inject it into the DOM tree:
var script = document.createElement('script'),
scripts = document.getElementsByTagName('script')[0];
script.src = url;
scripts.parentNode.insertBefore(script, scripts);
The returned JavaScript file is executed automatically by the browser. Loading the Facebook Like button and Google Analytics are two examples that make use of this technique. Tip: When such script files are requested on page load, it's recommended to use a standard script tag with the async
(and defer
) attribute included:
<script src="https://platform.twitter.com/widgets.js" async defer></script>
The HTML5 attribute async
tells the browser to load this script without blocking the page. defer
does essentially the same, but works on several older browsers, too.