facebook-login

#add these primary resources to include Facebook 
<div id="fb-root"></div>

# button for facebook
<button class="" onclick="_login();" ><i class="fa fa-facebook-official fa-2x" aria-hidden="true"></i>
  Continue with Facebook
</button>

# javascript/jquery
<script type="text/javascript">
	// Load the SDK asynchronously
	(function(thisdocument, scriptelement, id) {
		var js, fjs = thisdocument.getElementsByTagName(scriptelement)[0];
		if (thisdocument.getElementById(id)) return;

		js = thisdocument.createElement(scriptelement); js.id = id;
		js.src = "//connect.facebook.net/en_US/sdk.js";
		fjs.parentNode.insertBefore(js, fjs);
	}(document, 'script', 'facebook-jssdk'));

	window.fbAsyncInit = function() {
		FB.init({
			appId      : '{{your-fb-api-key}}',
			cookie     : true,
			xfbml      : true,
			version    : 'v3.3'
		});

	};

	// This is called with the results from from FB.getLoginStatus().
	function statusChangeCallback(response) {
		if (response.status === 'connected') {
			// Logged into your app and Facebook.
			_i();
		} else if (response.status === 'not_authorized') {
			// The person is logged into Facebook, but not your app.
			document.getElementById('status').innerHTML = 'Please log ' +
				'into this app.';
		}
	}

  //  called on click of button
	function _login() {
		FB.login(function(response) {
      // handle the response
			if(response.status==='connected') {
        // inbuilt function to login to my application as facebook is conntected to out application
        _i();
			}
		}, {scope: 'public_profile,email'});
	}
  
	function fb_logout(){
		FB.logout(function(response) {
			alert('logged out successfully');
		});
	}

	//facebook login
	function _i(){
		FB.api('/me?fields=email,name,picture', function(response) {
    // for more reference of fields 
    // https://developers.facebook.com/docs/facebook-login/permissions#reference-default
			
			$.post("localhost/login/validate", 
      {
        facebook_login: 'true', 
        email: response.email, 
        name: response.name, 
        fb_id:response.id, 
        photo:response.picture 
      }, 
      function(data){
				data = JSON.parse(data);
        // redirect as per success in data
			});
		});
	}
</script>