Facebook login using javascript-sdk

Its is very interesting and simple way to create a login flow using facebook api in our web app. So lets enjoy this code.
Step 1.

Create a directory structure like this:
root
——-index.php
——-home.php
——-fbscript.js

Step 2.

Before starting your code you have to create a facebook app.
Click Create a facebook app
Please follow facebook app developer guide line.
After finishing this app move to step 3.

Step 3.

In step 3
paste the following code in fbscript.js which you have created in Step 1.

  function statusChangeCallback(response) {
    console.log('statusChangeCallback');
    console.log(response);
    // The response object is returned with a status field that lets the
    // app know the current login status of the person.
    // Full docs on the response object can be found in the documentation
    // for FB.getLoginStatus().
    if (response.status === 'connected') {
      // Logged into your app and Facebook.
      testAPI();
    } 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.';
    } else {
      // The person is not logged into Facebook, so we're not sure if
      // they are logged into this app or not.
      document.getElementById('status').innerHTML = 'Please log ' +
        'into Facebook.';
    }
  }

  // This function is called when someone finishes with the Login
  // Button.  See the onlogin handler attached to it in the sample
  // code below.
  function checkLoginState() {
    FB.getLoginStatus(function(response) {
      statusChangeCallback(response);
    });
  }

  window.fbAsyncInit = function() {
  FB.init({
    appId      : '***********',// set you app id here
    cookie     : true,  // enable cookies to allow the server to access
                        // the session
    xfbml      : true,  // parse social plugins on this page
    version    : 'v2.1' // use version 2.1
  });

  // Now that we've initialized the JavaScript SDK, we call
  // FB.getLoginStatus().  This function gets the state of the
  // person visiting this page and can return one of three states to
  // the callback you provide.  They can be:
  //
  // 1. Logged into your app ('connected')
  // 2. Logged into Facebook, but not your app ('not_authorized')
  // 3. Not logged into Facebook and can't tell if they are logged into
  //    your app or not.
  //
  // These three cases are handled in the callback function.

  FB.getLoginStatus(function(response) {
    statusChangeCallback(response);
  });

  };

  // Load the SDK asynchronously
  (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'));

  // Here we run a very simple test of the Graph API after login is
  // successful.  See statusChangeCallback() for when this call is made.
  function testAPI() {
    console.log('Welcome!  Fetching your information.... ');
    FB.api('/me', function(response) {
      console.log('Successful login for: ' + response.name);
      document.getElementById('status').innerHTML =
        'Thanks for logging in, ' + response.name + '!';
    });
  }

Afetr you need to update the line

// set your facebook app id here.  you can see your app id is facebook app dashbord
  appId      : '***********',// set you app id here

Step 4.
Paste the following code in index.php

<!DOCTYPE html>
<!--
To change this license header, choose License Headers in Project Properties.
To change this template file, choose Tools | Templates
and open the template in the editor.
-->
<html>
    <head>
        <meta charset="UTF-8">
        <title>Facebook</title>
         
        <script src="http://code.jquery.com/jquery-1.11.1.min.js"></script>
         
 
         
    </head>
    <body>
    <script src="fb.js">  </script>     
 
<!--
  Below we include the Login Button social plugin. This button uses
  the JavaScript SDK to present a graphical Login button that triggers
  the FB.login() function when clicked.
-->
 
<fb:login-button scope="public_profile,email" onlogin="checkLoginState();">
</fb:login-button>
 
<div id="status">
</div>
          
         
    </body>
</html>

Step 5.
Paste the following code in home.php

       <!DOCTYPE html>
<!--
To change this license header, choose License Headers in Project Properties.
To change this template file, choose Tools | Templates
and open the template in the editor.
-->
<html>
    <head>
        <meta charset="UTF-8">
        <title>facebook home page</title>
 
        <script src="http://code.jquery.com/jquery-1.11.1.min.js"></script>
       
    </head>
    <body>
    <script>
    window.fbAsyncInit = function() {
  FB.init({
    appId      : '************',
    cookie     : true,  // enable cookies to allow the server to access 
                        // the session
    xfbml      : true,  // parse social plugins on this page
    version    : 'v2.1' // use version 2.1
  });
 
  // Now that we've initialized the JavaScript SDK, we call 
  // FB.getLoginStatus().  This function gets the state of the
  // person visiting this page and can return one of three states to
  // the callback you provide.  They can be:
  //
  // 1. Logged into your app ('connected')
  // 2. Logged into Facebook, but not your app ('not_authorized')
  // 3. Not logged into Facebook and can't tell if they are logged into
  //    your app or not.
  //
  // These three cases are handled in the callback function.
 
  FB.getLoginStatus(function(response) {
    statusChangeCallback(response);
  });
 
  };
 
  // Load the SDK asynchronously
  (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'));
   
  function statusChangeCallback(response) {
    // The response object is returned with a status field that lets the
    // app know the current login status of the person.
    // Full docs on the response object can be found in the documentation
    // for FB.getLoginStatus().
    if (response.status === 'connected') {
      // Logged into your app and Facebook.
       
    } else if (response.status === 'not_authorized') {
      // The person is logged into Facebook, but not your app.
      window.location.assign("index.php");
       
    } else {
      // The person is not logged into Facebook, so we're not sure if
      // they are logged into this app or not.
      window.location.assign("index.php");
       
    }
  }
   
    </script>
<button id="logout" class="button">
        Logout
    </button>
         
    <script>
    $(document).ready(function (){
        $("#logout").on('click', function (){
            FB.getLoginStatus(function(response) {
            if (response && response.status === 'connected') {
                    FB.logout(function(response) {
                    window.location.reload();
                    });
            }
            });
       });
   });
   </script>        
    </body>
</html>

Note: When you deploy this folder on remote server please set platform url in facebook app.

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