title: find the array index of an object with a specific key value in underscore
body: <p>In underscore, I can successfully find an item with a specific key value</p>
  
  <pre><code>var tv = [{id:1},{id:2}]
  var voteID = 2;
  var data = _.find(tv, function(voteItem){ return voteItem.id == voteID; });
  //data = { id: 2 }
  </code></pre>
  
  <p>but how do I find what array index that object occurred at?</p>