title: Backbone filter multiple collections on multiple attributes
body: <p>I am hoping some can help me, I have managed to create a tool that searches/filters a collections models based on various attributes (basically all the attributes of a model).</p>
  
  <pre><code>filterUsers: function (collection, filterValue) {
      var filteredCollection;
  
      if (filterValue === "") {
          return collection.toJSON();
      }
  
      return filteredCollection = collection.filter(function (data) {
  
          return _.some(_.values(data.toJSON()), function (value) {
  
              if (value != undefined) {
  
                  value = (!isNaN(value) ? value.toString() : value);
                  //var re = /^(([^&lt;&gt;()[\]\\.,;:\s@\"]+(\.[^&lt;&gt;()[\]\\.,;:\s@\"]+)*)|(\".+\"))@((\[[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\])|(([a-zA-Z\-0-9]+\.)+[a-zA-Z]{2,}))$/;
  
                  return value.indexOf(filterValue) &gt;= 0;
  
              }
  
          });
  
      });
  
  }
  </code></pre>
  
  <p>Now this works fine, for one collection, but is it possible to filter of multiple (2) collections? And return a merged set of results?</p>