Angular Reactive Forms Example: Building Dynamic and Interactive Web Forms

Angular Reactive Forms are a powerful feature that allows developers to create highly interactive and dynamic web forms. They offer a robust set of features which enable data binding, validation, and the ability to create custom form controls. By using Reactive Forms, developers can create complex and highly customized forms while maintaining the simplicity of HTML.

In this article, we will explore the fundamental concepts of Reactive Forms and walk through a practical example to create a dynamic form. We’ll also cover some frequently asked questions about Angular Reactive Forms.

Understanding Reactive Forms in Angular

Reactive Forms are an approach to building forms in Angular which are built around reactive programming concepts. In Reactive Forms, the form elements are defined as streams of data that can be observed and manipulated when changes occur.

The reactive programming approach allows developers to easily manage complex and dynamic forms. Instead of relying on imperative programming, Reactive Forms use declarative programming to describe the desired behavior. The advantage of this approach is that it provides a seamless integration of the form data between the UI and the Angular component.

At its core, Reactive Forms consist of three fundamental components:

1. FormBuilder: It is an Angular service that provides a set of functions that allow developers to create FormControl, FormGroup, and FormArray instances to represent the form model.

2. FormControl: It is a fundamental building block of Reactive Forms. It represents an individual form control and can be used to capture and validate the user input.

3. FormGroup: It is a collection of FormControl instances and represents a form group. It can be used to group related form controls together.

Building a Dynamic Form using Reactive Forms

To better understand how Reactive Forms work, let’s walk through an example of building a dynamic form using Reactive Forms. In this example, we will create a form that can capture personal information such as Name, Email, and Phone Number, and display the form data on the UI in real-time.

Step 1: Creating the Angular Component

To create the Angular component, run the following command in the terminal:

ng generate component demo-form

This command generates a component folder and files with the corresponding name of the component. In this example, the component name is “demo-form”.

Step 2: Importing Necessary Libraries

Before creating the form using Reactive Forms, we need to import the necessary libraries required for Reactive Forms:

import { FormBuilder, FormGroup, Validators } from ‘@angular/forms’;

Step 3: Creating the Reactive Form

Now let’s create the Reactive Form using the FormBuilder, FormGroup, and FormControl instances. Add the following code to your component file:

demoForm: FormGroup;

constructor(private fb: FormBuilder) {}

ngOnInit() {
this.demoForm ={
name: [”, Validators.required],
email: [”, [Validators.required,]],
phone: [”, Validators.required]

In the above code snippet, we first import the FormBuilder, FormGroup, and Validators classes from the ‘@angular/forms’ library.

Next, we create an instance of the FormGroup by calling the function. Inside the function, we define the three form inputs: Name, Email, and Phone Number. Each input is defined as a FormControl instance, and we specify any required validation rules using the Validators class.

Once we’ve created the FormGroup, we can bind it to our HTML template to begin building our dynamic form.

Step 4: Binding the Form to the HTML Template

Now we will bind our FormGroup instance to the HTML template. Add the following code to your HTML file:


{{ demoForm.value | json }}


In the above code snippet, we bind the FormGroup instance (demoForm) to the

element using the [formGroup] directive. We then define the form inputs using tags and specify each input with their respective formControlName.

Finally, we use the Angular JSON pipe (| json) to display the form data on the UI. This allows us to see the form data in real-time as it is entered in the form inputs.

Step 5: Validating Form Input

Reactive Forms can also validate form input to ensure the data entered meets certain criteria. In this example, we have added three form inputs, each with its own set of validation rules defined in the FormGroup instance.

For example, the “name” input requires that the user enters their name, and if the field is empty, the form will display an error message.

To display the validation error message on the UI, we add the following code to the HTML file:


Name is required


In the above code snippet, we use the *ngIf directive to display the error message only when the name input is invalid. We also check if the input has been touched or dirty, meaning that the user has tried to interact with the input.

The FormBuilder provides a wide range of validation rules that can be used to validate form input.


Q1. What is the difference between template-driven forms and reactive forms in Angular?

Template-driven Forms and Reactive Forms are two ways of building forms in Angular. Template-driven Forms use a simpler syntax that involves binding form inputs to a model object. Reactive Forms use a more robust and flexible approach, using a reactive programming model to define and manage form inputs.

Q2. What is a FormBuilder in Angular Reactive Forms?

The FormBuilder in Angular Reactive Forms is a service that provides functions for creating instances of FormControl, FormGroup, and FormArray. The FormBuilder simplifies the process of defining a Reactive Form by providing a concise and intuitive API for creating and managing form input streams.

Q3. How do I validate form data in Angular Reactive Forms?

To validate form data in Angular Reactive Forms, developers can use the Validators class provided by Angular. Validators is a static class that provides several built-in validation functions that can be used to validate form input. Developers can also define custom validation functions to validate form input in a more specific way.


Reactive Forms in Angular are a powerful and flexible way to create dynamic and complex web forms. By leveraging the reactive programming model, developers can create highly interactive forms with ease. The Angular FormBuilder simplifies the process of creating Reactive Forms, and the Validators class makes validating form data easy and intuitive.

In this article, we have walked through a complete example of building a dynamic form using Reactive Forms in Angular. We hope this article provides you with a solid foundation to get started with Reactive Forms.

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