jQuery-FB-button.js

$(document).ready(function() {
  $.ajaxSetup({ cache: true });
  $.getScript('//connect.facebook.net/en_US/sdk.js', function(){
    FB.init({
      appId: '{your-app-id}',
      version: 'v2.7' // or v2.1, v2.2, v2.3, ...
    });     
    $('#loginbutton,#feedbutton').removeAttr('disabled');
    FB.getLoginStatus(updateStatusCallback);
  });
});