title: Emulate Javascript 'alert' blocking nature
body: <p>Is it possible to create a custom modal message which 'blocks' the execution of the script until a user input?</p>
  
  <p>For example, how can you achieve this without using the native window alert / prompt functions?</p>
  
  <pre><code>setInterval(function(){ 
       alert('Click OK to Continue');  // timing stops until user hits ok
  },4000);
  </code></pre>
  
  <p>I know you could have your custom dialog invoke a callback function on user input, but I'm interested in being able to force this blocking behaviour</p>