Edit in JSFiddle

;(function($, window, document, undefined){

    $(function(){

        // mixi
        $.getScript('//static.mixi.jp/js/plugins.js#lang=ja');

        // twitter
        $.getScript('//platform.twitter.com/widgets.js');

        // facebook
        (function(){
            if(window.FB){
                FB.init({ cookie: true, xfbml: true });
            }else{
                $.getScript('//connect.facebook.net/ja_JP/all.js', function(){
                    FB.init({ cookie: true, xfbml: true });
                });
            };
        }());

    });

}(jQuery, window, this.document));

<!-- mixi -->
<div 
    data-plugins-type="mixi-favorite"
    data-service-key="15d1190b592fc08421499d8abc1f9e2d9e1a2858"
    data-size="medium"
    data-href=""
    data-show-faces="false"
    data-show-count="true"
    data-show-comment="false"
    data-width=""></div>

<!-- twitter -->
<a
    href="https://twitter.com/share"
    class="twitter-share-button"
    data-lang="ja">ツイート</a>

<!-- facebook -->
<div
    class="fb-like"
    data-send="false"
    data-layout="button_count"
    data-show-faces="false"
    data-font="verdana"></div>