rexm

var MyBigVM = function (options) {
  var $koThis = this;
  var map = {
    Items: {
        create: function(options) {
            var item = ko.mapping.fromJS(options.data);
            item.blaComputed = ko.computed(function () {
                return this.bla1() + " / " + this.bla12();
            }, item);
            return item;