Optimised async loading of cross-domain scripts See also : http://css-tricks.com/thinking-async/

async.js

// source : https://gist.github.com/necolas/1025811
/*
 * Updated to use the function-based method described in http://www.phpied.com/social-button-bffs/
 * Better handling of scripts without supplied ids.
 *
 * N.B. Be sure to include Google Analytics's _gaq and Facebook's fbAsyncInit prior to this function.
 */

(function(doc, script) {
    var js, 
        fjs = doc.getElementsByTagName(script)[0],
        add = function(url, id) {
            if (doc.getElementById(id)) {return;}
            js = doc.createElement(script);
            js.src = url;
            js.async = 'async';
            id && (js.id = id);
            fjs.parentNode.insertBefore(js, fjs);
        };

    // Google Analytics
    add('//www.google-analytics.com/analytics.js', 'ga');
    // Google+ button
    add('https://apis.google.com/js/plusone.js');
    // Facebook SDK
    add('//connect.facebook.net/en_US/all.js', 'facebook-jssdk');
    // Twitter SDK
    add('//platform.twitter.com/widgets.js', 'twitter-wjs');
    // Livereload snippet
    add('http://' + (location.host || 'localhost').split(':')[0] + ':8000/livereload.js?snipver=1', 'livereload');
}(document, 'script'));

in-garber-irish.js

// Function
_universalAsync : function(url, id){
    var js,
    fjs = document.getElementById('basejs'),
    add = function(href, idScript) {
        if (document.getElementById(idScript)) {return;}
        js = document.createElement('script');
        js.async = 'async';
        js.src = href;
        idScript && (js.id = idScript);
        fjs.parentNode.insertBefore(js, fjs);
    };
    add(url, id);
}

// Call
UTIL._universalAsync('url', 'optionnal-id');