Angular Web Framework Reactive Forms & Validation 3

Question 1

Which operator is commonly used to debounce a reactive form's `valueChanges` observable before making an HTTP call?

Accepted Answer

debounceTime()

Answer

`debounceTime()` waits for a specified quiet period after the last emission before forwarding the value, reducing unnecessary API calls.

Question 2

In a cross-field validator, where should you attach the validator to validate that `password` and `confirmPassword` match?

Accepted Answer

On the parent FormGroup

Answer

Cross-field validators are attached to the FormGroup so they have access to all sibling controls.

Question 3

What is the return type of a valid (passing) custom validator function?

Accepted Answer

null

Answer

A validator must return `null` when the control is valid; any non-null object signals an error.

Question 4

Which FormArray method removes the control at a given index?

Accepted Answer

removeAt(index)

Answer

`FormArray.removeAt(index)` removes the control at the specified position and updates the array's validity.

Question 5

How does Angular determine whether an async validator is still pending?

Accepted Answer

The control's status is 'PENDING'

Answer

While async validators are running, the control's `status` property is set to `'PENDING'`.

Angular Web Framework Practice Test