You could use Google Analytics or Facebook‘s method:
(function(d, script) {
script = d.createElement('script');
script.type="text/javascript";
script.async = true;
script.onload = function(){
// remote script has loaded
};
script.src="http://www.google-analytics.com/ga.js";
d.getElementsByTagName('head')[0].appendChild(script);
}(document));
UPDATE:
Below is the new Facebook method; it relies on an existing script tag instead of <head>
:
(function(d, s, id){
var js, fjs = d.getElementsByTagName(s)[0];
if (d.getElementById(id)){ return; }
js = d.createElement(s); js.id = id;
js.onload = function(){
// remote script has loaded
};
js.src = "https://connect.facebook.net/en_US/sdk.js";
fjs.parentNode.insertBefore(js, fjs);
}(document, 'script', 'facebook-jssdk'));
- Replace
facebook-jssdk
with your unique script identifier to avoid it being appended more than once. - Replace the script’s url with your own.