title: unable to update
body: <p>i got the below code, which i have a problem with.
  I'm unable to calculate the 'total' amount on any instances of 'Labouritems' apart from the first instance, each on after that i'm not getting it to calculate.</p>
  
  <pre><code>var LabourItems = {
     rate: null,
     hours: null,
     total: null,
     init: function(object) {
        this.rate = parseInt($(object).children('.rate').first().val(), 10);
        // var rate = $(object).children('.rate').first();
        this.hours =parseInt($(object).children('.hours').first().val(), 10);
        this.total = this.rate * this.hours;
        this.updateTotal(object);
     },
     updateTotal: function(object) {
        $(object).children('.total').first().val(this.total || 0);
     }
  }
  
  //reactTochange for those inputs that you want to observe
  $('.labouritems input').on("keyup", function() {
     $('.labouritems').each( function(key,value){
        LabourItems.init(this);
     });
  });
  </code></pre>