MEAN Angular Routing and Forms 3

Question 1

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

Accepted Answer

FormControl

Answer

FormInput

Answer

ReactiveControl

Answer

NgControl

Question 2

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

Accepted Answer

FormBuilder

Answer

ReactiveFormService

Answer

FormGroup

Answer

FormFactory

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

new FormControl('', 'required,minLength(3)')

Answer

new FormControl('', { validate: ['required', 'minLength'] })

Answer

new FormControl('', Validators.required() & Validators.minLength(3))

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

To define a fixed set of named form fields

Answer

To validate multiple fields simultaneously with a shared validator

Answer

To group related controls under a common parent with shared state

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() works on FormControl only; patchValue() works on FormGroup only

Answer

setValue() triggers validation immediately; patchValue() defers validation

Answer

setValue() is synchronous; patchValue() returns a Promise

Question 6

Which method do you call on a FormControl or FormGroup to check if a specific validation error exists?

Accepted Answer

formGroup.get('field').hasError('required')

Answer

formGroup.controls['field'].checkError('required')

Answer

formGroup.validate('field', 'required')

Answer

formGroup.getError('field', 'required')

Question 7

How do you bind a reactive FormGroup instance to a <form> element in an Angular template?

Accepted Answer

[formGroup]="myForm"

Answer

[ngModel]="myForm"

Answer

[ngFormGroup]="myForm"

Answer

(formGroup)="myForm"