title: How does AngularJS know when variables change? How does AngularJS dirty checking work?
body: <p>I was reading some article to understand a little bit more how AngularJS works.</p>
  
  <p>One of the terms that I didn't understand is <code>Dirty Checking</code>. </p>
  
  <p>What is it exactly? It seems like the Observer pattern but apparently it's better.</p>
  
  <p>Can you help me understand this please?</p>
  
  <p>EDIT : it can be also useful for people who wants to learn more about that to watch <a href="https://www.youtube.com/watch?v=Mk2WwSxK218" rel="noreferrer">this video</a> from <a href="https://github.com/Swiip" rel="noreferrer">swiip</a> at NgEurope some years ago.</p>