demoScript.html

    <script async defer crossorigin="anonymous" src="https://connect.facebook.net/he_IL/sdk.js#xfbml=1&version=v6.0&appId=811987785971081&autoLogAppEvents=1"></script>
    <script>
        window.fbAsyncInit = function() {
            FB.init({
                xfbml: true,
                version: 'v6.0'});
            FB.getLoginStatus(function (response) {
                if (response.status === 'connected') {
                    var e = document.getElementById("logintofb");
                    e.parentNode.removeChild(e);}});
            (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 = 'https://connect.facebook.net/he_IL/sdk/xfbml.customerchat.js';
                fjs.parentNode.insertBefore(js, fjs);
            }(document, 'script', 'facebook-jssdk'));
            if (response.status === 'connected') {
                FB.Event.subscribe('send_to_messenger',
                        function (e) {console.log(e);});
            }
        }
    </script>