angular2 dynamic form calculate amount total

Question

Trying to calculate a total payOffs.amount (payOffs is a FormArray). Not sure how to do it properly so the total would observe changes to current and new for amounts. Here i

Answer 1

Or you could observe changes on the whole form array, by subscribing to the changes in the constructor.

this.form.controls.payOffs.valueChanges.subscribe((change) => {
  const calculateAmount = (payoffs: any[]): number => {
    return payoffs.reduce((acc, current) => {
       // also handling case when a new pay off is added with amount of null
       return acc + parseFloat(current.amount || 0);
    }, 0);
  }

  console.log(calculateAmount(this.form.controls.payOffs.value));
});