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This post lists some subjective questions and answers related to Angular Reactive Forms. This collection contains some potential interview questions that may be helpful if you are preparing for a Frontend Engineering job interview specific to Angular framework. Check out Angular Interview Series – Topic Wise Q&A.
1. What are Reactive Forms in Angular?
Reactive Forms are a way to manage form controls and their validation in a reactive manner, using an explicit and immutable approach to managing form state.
2. How do you create a Reactive Form?
We create a Reactive Form by importing ReactiveFormsModule, then using FormGroup and FormControl in our component to define the form structure.
3. What is FormGroup?
FormGroup is a class that tracks the value and validity of a group of FormControl instances, representing a form in a structured way.
4 What is FormControl?
FormControl is a class that represents a single input element in a form, managing its value, validation status, and change events.
5. How do you add validation to a Reactive Form?
We can add validation by passing validation functions to FormControl or FormGroup during initialization, e.g., new FormControl('', Validators.required).
6. What is the purpose of FormBuilder?
FormBuilder is a service that simplifies the creation of FormGroup and FormControl instances, providing a more concise API for building forms.
7. How do you access form values in Reactive Forms?
We can access the values of a FormGroup using the value property, e.g., this.formGroup.value, where formGroup is your defined FormGroup.
8. How can you react to form changes in Reactive Forms?
We can subscribe to value changes using the valueChanges observable, e.g.
this.formGroup.valueChanges.subscribe(value => {
/* handle changes */
}).9. What is the difference between Reactive Forms and Template-driven Forms?
Reactive Forms provide a more programmatic approach with explicit control over form data and validation, while Template-driven Forms rely on Angular directives in templates and are more declarative.
10. How do you reset a Reactive Form?
We can reset a Reactive Form by calling the reset() method on the FormGroup.
These are a few questionnaires specific to Angular’s Reactive Forms. I will be adding more questions and answers to this post. To know more details please refer to the Official documentation on Angular Reactive Forms.