Inspired by http://socialitejs.com/, asynchronously load twitter/facebook scripts based on event

async-social.js

$(function($) {
    'use strict';
    var srcs = {
        twitter: {
            id: 'Twitter',
            get: function(d, s, id) {
                var js, fjs = d.getElementsByTagName(s)[0];
                if (!d.getElementById(id)) {
                    js = d.createElement(s);
                    js.id = id;
                    js.src = "//platform.twitter.com/widgets.js";
                    fjs.parentNode.insertBefore(js, fjs);
                }
            },
            hasLoaded: false
        },
        facebook: {
            id: 'Facebook',
            get: function(d, s, id) {
                var js, fjs = d.getElementsByTagName(s)[0];
                if (d.getElementById(id)) return;
                js = d.createElement(s);
                js.id = id;
                js.src = "//connect.facebook.net/en_US/all.js#xfbml=1&appId=${fb_app_id}";
                fjs.parentNode.insertBefore(js, fjs);
            },
            hasLoaded: false
        }
    };


    function load(src, args) {
        if (!src.hasLoaded) {
            src.get.apply(null, args);
            src.hasLoaded = true;
            //console.log(src.id + ' loaded');
        }
    }

    var share = {
        tweet: function() {
            load(srcs.twitter, [document, "script", "twitter-wjs"]);
        },
        fb: function() {
            load(srcs.facebook, [document, "script", "facebook-jssdk"]);
        }
    };

    $(window).on('scroll', function() {
        share.tweet();
        share.fb();
    });
});