title: how to set my own message on beforeunload event
body: <p>how to set my own message here, on my own language<br />
  Whatever is set as <code>returnValue</code> the resulting message is <code>Changes you made may not be saved.</code></p>
  <pre><code>window.addEventListener(&quot;beforeunload&quot;, function(event){
      if(saved == false){
          event.preventDefault();
          event.returnValue = &quot;You didn't save changes&quot;;
      }
  });
  </code></pre>