Extending the product model

To validate our models using the Knockout Validation library, we are going to extend our model's attributes. Extenders are a basic feature of Knockout. Using extenders we can add some properties to our observables to increase their behavior. For more information on extenders, please refer to the following link:

http://knockoutjs.com/documentation/extenders.html

We are going to extend our product model with some properties that will allow us to validate data by following these steps:

1. Go to the models/Product.js file.

2. Update the name field. It should have at least three letters and should contain just letters, numbers, and dashes:

   _name = ko.observable(name).extend({
     required: true,
     minLength: 3,
     pattern: {
       message: 'Hey this doesn\'t match my pattern',
       params: '^[A-Za-z0-9 \-]+$'
     }
   })

3. Update the price to allow just numbers, and set a range (maximum and minimum values) for it:

   _price = ko.observable(price).extend({
     required: true,
     number:true,
     min...