title: Pass data from one model to another in Backbone
body: <pre><code>&lt;form&gt;
    &lt;input id = "one" class = "number"&gt;
    &lt;input id = "two" class = "number"&gt;
    &lt;input id = "three" class = "number"&gt;
    &lt;input id = "four" class = "number"&gt;
  &lt;/form&gt;
  </code></pre>
  
  <p>in a model.</p>
  
  <p>I have a button which has the following function:</p>
  
  <pre><code>$("#button").click(function(){
    var mynumber = $("#one").val() + $("#two").val() + $("#three").val();
    //IF i do a this.model.save here it will POST all four fields that I dont want
  });
  </code></pre>
  
  <p>Question: I want to create a new model which gets this value mynumber and do a POST request. So far I have this:</p>
  
  <pre><code>var mymodel = Numbermodel.extend({
    this.model.set(mynumber);
    this.model.save({},{
      success: function(model, response) {
        console.log('success! ' + response);
      },
      error: function(model, response) {
        console.log('error! ' + response);
      }
    });
  });
  </code></pre>
  
  <p>I am not sure how I can connect these two. I just want to POST mynumber not all the individual fields. Any help would be appreciated?</p>