Working javascript example - facebook sdk 4.0

<button id="loginBtn">Facebook Login</button>
<div id="response"></div>

<script>
    function getUserData() {
    FB.api('/PAGE-ID/posts', function(response) {
        console.log(response.data);
       console.log(response.data.length)
       for (var i=0, l=response.data.length; i<l; i++) {
          var post = response.data[i];
          console.log(post)
          if (post.message) {
             console.log('Message: ' + post.message);
          } else if (post.attachment && post.attachment.name) {
             console.log('Attachment: ' + post.attachment.name);
          }
       }
    });
}

window.fbAsyncInit = function() {
    //SDK loaded, initialize it
    FB.init({
        appId      : 'APP-ID',
        xfbml      : true,
        version    : 'v2.2'
    });

    //check user session and refresh it
    FB.getLoginStatus(function(response) {
        if (response.status === 'connected') {
            //user is authorized
            document.getElementById('loginBtn').style.display = 'none';
            getUserData();
        } else {
            //user is not authorized
        }
    });
};

//load the JavaScript SDK
(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'));

//add event listener to login button
document.getElementById('loginBtn').addEventListener('click', function() {
    //do the login
    FB.login(function(response) {
        if (response.authResponse) {
            //user just authorized your app
            document.getElementById('loginBtn').style.display = 'none';
            getUserData();
        }
    }, {scope: 'read_stream', return_scopes: true} // depending on the information we want to retrieve, we might need to set permissions
 );
}, false);

</script>