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Knockout JS Mapping fromJS nested models

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I am having trouble understanding how to work with Knockout JS Mapping Plugin. I have some nested models (as seen below) and what I am currently doing is just using the ko.mapping.fromJS() in the parent model. What I am noticing is that computed values are not being ...computed.

I tried to understand the "create":

var mapping = {     'children': {         create: function(options) {             return new myChildModel(options.data);         }     } } var viewModel = ko.mapping.fromJS(data, mapping); 

But right now in my current scenario I am not sure how to implemented.

Current structure:

var ProductModel = function($name, $price, $quantity) {     var self = this;      self.id = ko.observable();     self.name = ko.observable($name);     self.quantity = ko.observable($quantity);     self.price = ko.observable($price);     self.price.total = ko.computed(function() {         return self.price() * self.quantity();     }); };   var CartModel =  function (){    var self = this;     // Model Properties    self.id = ko.observable();       self.products = ko.observableArray();         self.fetch = function() {         $.ajax({             url: "route to get the specific cart",             type: "GET",             success: function(data) {                                 ko.mapping.fromJS(data, {}, self);             }         });     };         // Convert to mapping format     ko.mapping.fromJS(ko.mapping.toJS(self)); };  var ViewModel = ko.validatedObservable(new CartModel()); ko.applyBindings(new ViewModel()); 

I am not sure how to get the ProductModel to trigger the computed inside the ProductModel, I am not sure if I have to call the ko.mapping.fromJS inside every single Model (I have many more models, I stripped them out to make it simpler).

After the fetch function I alerted the products().length and it actually contains the quantity that was previously saved. but the computed is not showing. How do I implement the create method of knockout mapping plugin for nested observable(and observablearrays) that are models with computed inside of them.

P.S: The reason I have it self.price.total is in order to avoid the toJS send the total key as well. I can't ignore the properties of nested models using ignore:

See this thread for more: Knockout JS Mapping fromJS nested models


How does your ajax response looks like? Does it returns the whole cart, or just the products?

Anyway, if you want to handle your product list as an observableArray of viewmodels you could do something like this:

ko.utils.arrayForEach(products, function(item, index) {
  self.products.push(new ProductModel(item.name, item.price, item.qty);

If you want to use the mapping plugin, I haven't made a custom implementation of the "create" method, but I would do something like:

var ProductModel = function(product) {
  var self = this;

  ko.mapping.fromJS(product, {}, self);

  self.total = ko.computed(function() {
      return self.price() * self.quantity();


I have re-read your question, and I think this answer may be what you're looking for, the only downside of that approach, well for me at least, is that you would need to define a mapping config object for each viewmodel with nested viewmodels in your code

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