title: Function return [Object Object] not the value
body: <p>I created this function and I don't know why it return <code>[Object Object]</code> and not the value that I got. The function should return a string like <code>(Main/121)</code>. However, the alert shows the value that I wanted.</p>
  
  <pre><code>module.Order = Backbone.Model.extend({
          initialize: function (attributes) {
              Backbone.Model.prototype.initialize.apply(this, arguments);
              this.pos = attributes.pos;
              var that = this;
              this.sequence_number = this.pos.pos_session.sequence_number++;
              debugger;
              this.uid = this.generateUniqueId();
              this.pro = this.get_the_other_main();
              this.set({
                  creationDate: new Date(),
                  orderLines: new module.OrderlineCollection(),
                  paymentLines: new module.PaymentlineCollection(),
                  name: _t("Order ") + this.uid,
                  client: null,
                  sales_person: null,
                  sales_person_name: null,
                  new_id: this.pro
              });
              this.selected_orderline = undefined;
              this.selected_paymentline = undefined;
              this.screen_data = {};  // see ScreenSelector
              this.receipt_type = 'receipt';  // 'receipt' || 'invoice'
              this.temporary = attributes.temporary || false;
              return this;
          },
        get_the_other_main: function (callback) {
             return new instance.web.Model("pos.order").call('get_the_product', []).done(
                   function(results) {
                      var result = results.toString().split(',');
                       var stringsl=result[1];
                       var thenum = stringsl.replace( /^\D+/g, '');
                       var sasa=parseInt(thenum,10)+1
                       var zika=('00' + sasa).slice(-4)
                       var the_str=result[1].slice(0,-4).toString();
                       var new_seq_sasa=the_str+zika
                       alert(new_seq_sasa)
                       return callback(new_seq_sasa);
                  }
  
              );
          },
  </code></pre>