Loading social scripts (Facebook, Twitter and Google Plus) AMD style.

social.js

/*jslint browser:true, nomen:true*/
/*global define*/

define(function () {
    'use strict';

    var script = document.getElementsByTagName('script')[0];

    function socialTag(src, id) {
        var created = document.createElement('script');

        if (id && document.getElementById(id)) {
            return;
        }

        created.type  = 'text/javascript';
        created.async = true;
        created.id    = id;
        created.src   = src;

        script.parentNode.insertBefore(created, script);
    }

    socialTag('//connect.facebook.net/pt_BR/all.js#xfbml=1&appId=378405708894505', 'facebook-jssdk');
    socialTag('//platform.twitter.com/widgets.js', 'twitter-wjs');
    socialTag('//apis.google.com/js/plusone.js');
});