FB Javascript SDK

HTML

<fb:login-button scope="public_profile,email" onlogin="checkLoginState();"></fb:login-button>

<div id="status"></div>

JavaScript

window.fbAsyncInit = function() {
  FB.init({
    appId      : 1174852745906995,
    xfbml      : true,
    version    : 'v2.8'
  });
  FB.AppEvents.logPageView();


  FB.getLoginStatus(function(response) {
    if (response.status === 'connected') {
      console.log('Logged in.');
    }
    else {
      FB.login();
    }
  });


};

(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/sdk.js";
  fjs.parentNode.insertBefore(js, fjs);
}(document, 'script', 'facebook-jssdk'));