title: ng-repeat with track by over multiple properties
body: <p>I have a problem with angular ng-repeat directive.
  Currently I work on some project where from the API I get a list of items (some times it could be 1k items) and this list should be refreshed every 5 seconds (it is monitoring related project).</p>
  
  <p>When the list length is a little bigger the website while re-rendering DOM could "slow". It comes out that angular regenerate the whole DOM (but 95% of item are the same ! ) </p>
  
  <p>One of the possible approach is to set "track by" expression for example to item.id. But here comes another problem, I also want regenerate items when for example descriptions was changed by other user. Since track by is expression to item.id changes in item.description didn't update item in DOM.</p>
  
  <p>There is way to track by over multiple properties? Maybe some function?
  Or maybe do comparison by "hand" ?</p>
  
  <p>Any ideas, code samples I would appreciate :) </p>
  
  <p><strong>UPDATE</strong></p>
  
  <p>what I discover when I set track by to item.id angular didn't re-crete html for items, just update value in already created element and it seems to be "faster" then removing and creating. 
  Previously I though a little bit different. </p>
  
  <p><strong>FIX</strong></p>
  
  <p>For those who are looking for better performance over >1k items in <strong>ng-repeat</strong> USE <strong>track by item.id</strong> it will boost your performance ;) </p>