title: Multi-Property lookup with Backbone and Underscore
body: <p>I have a method on my collection called <code>activeCall</code> that takes an id as a parameter. This method does a <code>_find</code> with underscore and returns the first match. What I want to do is pass multiple parameters to the method, then have the <code>.get()</code> function use those params.</p>
  
  <p>Here's what I currently have:</p>
  
  <pre><code>var Activities = Backbone.Collection.extend({
      model: Activity,
      url: "/activity",
      activeCall: function (Activity_id) {
          return _.find(this.models, function (item) {
              return item.get("Activity_id") === Activity_id;
          });
      }
  });
  </code></pre>
  
  <p>Here is what I'd like to do:</p>
  
  <pre><code>var Activities = Backbone.Collection.extend({
      model: Activity,
      url: "/activity",
      activeCall: function (Activity_id, CallType_id) {
          return _.find(this.models, function (item) {
              //How do I use both Activity_id &amp; CallType_id with the call to item.get()?
              return item.get("Activity_id") === Activity_id &amp;&amp; item.get("CallType_id") === CallType_id;
          });
      }
  });
  </code></pre>