title: Dirty Checking in angular
body: <p>I was recently going through a pretty interesting article about <a href="https://stackoverflow.com/questions/9682092/how-does-data-binding-work-in-angularjs?rq=1">data binding in angularJS</a>.
  I came across a term there : 'Dirty-Checking', which is performed during a <code>$digest</code> operation. The term sounded quite interesting to me but unfortunately, didn't make much sense about what's dirty over there. Does it concern the constant check on some value ?</p>