Modifying forms dynamically
So far, we have used the FormGroup and FormControl classes extensively throughout this chapter. However, we have not seen what FormArray is all about. 
Consider the scenario where we have added some products to the shopping cart of our e-shop application and want to update their quantities before checking out the order.
Currently, our application does not have any functionality for a shopping cart, so we will now add one:
- Create a new service to manage the shopping cart by running the following Angular CLI command in the 
src\app\cartfolder:ng generate service cart - Open the 
cart.service.tsfile and add the followingimportstatement:import { Product } from '../products/product'; - Create a 
cartproperty in theCartServiceclass and initialize it to an empty array:...export class CartService { cart: Product[] = []; constructor() { } }