How to take default value in Reactive Form

Question

I want to Pass default value from HTML to Type script using reactive Form

<ul class="list list_2">
<li>Subtotal <span>{{cartTotal | currency:'INR':true:'2.0'}}</span></li>
<li>Shipping Charge<span>{{shipping | currency:'INR':true:'2.0'}}</span></li>
<li>Total <span><input type="text" value="{{cartTotal+shipping | currency:'INR':true:'2.0'}}" class="total" formControlName="TotalAmount" readonly></span></li>
</ul>

This is my HTML where i have given default value in input

get TotalAmount(){
    return this.billingForm.get("TotalAmount.value")

In type script i have this method for getting data and i am using Formgroup

billingForm=new FormGroup({
    Address:new FormControl('',[Validators.required]),
    City:new FormControl('',[Validators.required]),
    State:new FormControl('',[Validators.required]),
    Postcode:new FormControl('',[Validators.required]),
    TotalAmount:new FormControl(''),
    PayType:new FormControl('')
  })

I want to pass that default value but it always giving null

Answer 1

You should wrap things differently.

First, change your form's initialization.

Add FormBuilder as a dependency to your component's consctructor.

constructor(private builder: FormBuilder) {}

And use the builder to initialize your form.

    this.billingForm = this.builder.group({
      Address: new FormControl("", [Validators.required]),
      City: new FormControl("", [Validators.required]),
      State: new FormControl("", [Validators.required]),
      Postcode: new FormControl("", [Validators.required]),
      TotalAmount: new FormControl(""),
      PayType: new FormControl("")
    });

Then, your TotalAmount's HTML as:

<li>Total <span><input type="text" value="{{TotalAmount | currency:'INR':true:'2.0'}}" class="total" formControlName="TotalAmount" readonly></span></li>

So, when you are getting cartTotal from your db. Assign cartTotal+shipping to your TotalAmount FormControl. Like:

this.billingForm.get("TotalAmount").setValue(this.cartTotal + this.shipping);

And, change your TotalAmount property as:

   get TotalAmount() {
      return this.billingForm.get("TotalAmount").value;
   }

Sample:

Working demo at StackBlitz