MEAN Angular Routing and Forms 3

Question 1

Which class represents a single form input control in Angular reactive forms?

Accepted Answer

FormControl

Answer

FormControl is the most basic building block of reactive forms; it tracks the value, validation status, and interaction state of a single form input.

Question 2

Which injectable service provides shorthand factory methods for creating reactive form controls with less boilerplate?

Accepted Answer

FormBuilder

Answer

FormBuilder is an injectable service that provides group(), control(), and array() factory methods to simplify the creation of reactive form control trees.

Question 3

How do you apply multiple built-in validators to a FormControl in Angular reactive forms?

Accepted Answer

new FormControl('', [Validators.required, Validators.minLength(3)])

Answer

Validators are passed as the second argument to the FormControl constructor in an array; the Validators class provides static methods for all built-in validators.

Question 4

What is the primary purpose of FormArray in Angular reactive forms?

Accepted Answer

To manage a dynamic list of form controls or groups

Answer

FormArray manages a dynamic array of AbstractControl instances, making it ideal when users can add or remove fields at runtime.

Question 5

What is the key difference between setValue() and patchValue() on a reactive FormGroup?

Accepted Answer

setValue() requires values for all controls; patchValue() allows partial updates

Answer

setValue() throws an error if any control in the FormGroup is missing from the provided object, while patchValue() silently ignores any missing controls.

MEAN - Stack Development Practice Test

MEAN - Stack Development Practice Test

MEAN Angular Routing and Forms 3