Question

<div id="fb-root"></div><script>
(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/all.js#xfbml=1&appId=223245147771570";
fjs.parentNode.insertBefore(js, fjs);}
(document, 'script', 'facebook-jssdk'));
FB.Event.subscribe('edge.create',
function(response) {
    alert('You liked the URL: ' + response);
});</script>   
  <h1>Lajknout stranku!</h1>
  <div class="fb-like" data-href="https://www.facebook.com/Testra22" data-send="false" data-layout="button_count" data-width="10" data-show-faces="false" data-font="trebuchet ms"></div> 

I use this code to create FB Like button and I would like to display alert when user click on it. But there is js error Uncaught ReferenceError: FB is not defined.

Answer 1

You start using Facebook JS SDK before it was loaded by browser.

Because you use asynchronous way to load the JS SDK you need to define window.fbAsyncInit (as described in documentation for JavaScript SDK) function and run code that depend on JS SDK from here…

window.fbAsyncInit = function() {
  FB.Event.subscribe('edge.create', function(response) {
    alert('You liked the URL: ' + response);
  });
}