Codepointng...lets talk code: How to Login in Website With Facebook User Id and Password

This is a general question but important now a days for every developer. There is a defined step-by-step process for logging into a website through Facebook user id and password.

Log into your Facebook account and go to "Manage app".
Create new apps (if you have already an app).
Next.
If you want to make Sand box public then check the Disabled sandbox mood.
I will use a "<div>" for showing the login with Facebook button:

<div class="fb-Login">

<input type="button" id="btnFacebook" name="btnFacebook" value="" class="fb-Button" />

</div>
Then a "<script>" after the "<body>" tag:

<body >

<div id="fb-root"></div>

<script type="text/javascript" language="javascript" src="js/fb-Login.js"></script>
Then facebooklogoin.js:

     //Edited by dkp

        // Load the SDK Asynchronously

        (function (d) {

            var js, id = 'facebook-jssdk', ref = d.getElementsByTagName('script')[0];

            if (d.getElementById(id)) { return; }

            js = d.createElement('script'); js.id = id; js.async = true;

            js.src = "//connect.facebook.net/en_US/all.js#xfbml=1";

            ref.parentNode.insertBefore(js, ref);

        } (document));

        // Additional JS functions here

        window.fbAsyncInit = function () {

            FB.init({

                appId: '408537542603090',

                channelUrl: '//http://yoururl.com/channel.html',

                status: true,

                cookie: true,

                xfbml: true

            });

            FB.getLoginStatus(function (response) {

                if (response.status == 'connected') {

                    // window.location = "http://dubaibricks.com/siteuser/home.aspx";

                    //connected

                    //alert("You are already login with facebook userid and password.");

                } else if (response.status == 'not_authorized') {

                    alert("Please use normal signin with userid and password!Otherwise Provide us to fetch necessary informations from facebook like Email,date of birth.These are all private not public!")

                    FB.logout(function (response) {

                        //logout

                        alert("You are Signout successfully!Thank you.");

                    });

                    // not_authorized

                } else {

                    // not_logged_in

                    //window.location = "http://96.0.68.12/";

                }

            });

        };

        function login() {

            FB.login(function (response) {

                if (response.authResponse) {

                    Getloginuserdetails();

                } else {

                }

            }, { scope: 'email,user_birthday,user_location' });

        }

        function Getloginuserdetails() {

            FB.api('/me', function (response) {

                //alert('Welcome ' + response.first_name + ',' + response.last_name + ',' + response.gender + ',' + response.email + ',' + response.birthday);

                var date = new Date();

                var curyear = date.getFullYear();

                //var curmonth = date.getMonth()+1;

                //var curdate = date.getDate();

                //var datediff = parent()

                var yeardiff = parseInt(curyear) - parseInt(response.birthday.substr(6, 4))

                if (yeardiff < 18) {

                    alert("Your age must be 18 years or above")

                    FB.logout(function (response) {

                        // user is now logged out

                    });

                }

                else {

                    var data = response.first_name + "|" + response.last_name + "|" + response.email + "| |";

                    data += response.gender + "| |" + yeardiff + "|";

                    $.ajax({

                        type: "POST",

                        async: false,

                        url: "Handler/registration.ashx",

                        data: data,

                        beforeSend: function (xhr) { xhr.setRequestHeader("X-AjaxPro-Method", "REGISTRATION-FB"); },

                        success: function (response) {

                            window.location = response;

                        },

                        error: function (xhr) {

                            //alert(xhr.status)

                            //alert(xhr.statusText);

                            //alert(xhr.responseText);

                            alert("!Sorry im am not fething your essential information.Please Try again later.");

                        }

                    });

                }

            });

        }
The channel.html:

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">

<html xmlns="http://www.w3.org/1999/xhtml">

<head>

<title></title>

</head>

<body>

<script type="text/javascript" language="javascript" src="//connect.facebook.net/en_US/all.js"></script>

</body>

</html>
Screen like this:
Click "Sign in with Facebook":
Login with Facebook credentials in your website.