Angular 11 Form Validation example (Reactive Forms)

In this tutorial, I will show you how to implement Angular 11 Form Validation example (and Submit) with Reactive Forms Module and Bootstrap 4.

More Practice:
Angular 11 File upload example with progress bar
Angular 11 CRUD Application example with Web API
Angular 11 JWT Authentication example with Web Api

Serverless with Firebase:
Angular 11 Firebase CRUD Realtime DB | AngularFireDatabase
Angular 11 Firestore CRUD example | AngularFireStore
Angular 11 File Upload Firebase Storage: Display/Delete Files example


Overview of Angular 11 Form Validation example

We will implement validation for a Angular Form using Reactive Forms Module and Bootstrap. The form has:

  • Full Name: required
  • Username: required, from 6 to 20 characters
  • Email: required, email format
  • Password: required, from 6 to 40 characters
  • Confirm Password: required, same as Password
  • Accept Terms Checkbox: required

angular-11-form-validation-example-reactive-forms

Some fields could be wrong:

angular-11-form-validation-example-reactive-forms-check

Successful Submission will look like this:

angular-11-form-validation-example-reactive-forms-successful

Technology

We’re gonna use following modules:

  • Angular 11
  • Bootstrap 4
  • @angular/forms 11

Setup Project

First we need to add the ReactiveFormsModule into our App Module.

Open src/app/app.module.ts and import ReactiveFormsModule from @angular/forms:

import { NgModule } from '@angular/core';
import { BrowserModule } from '@angular/platform-browser';
import { ReactiveFormsModule } from '@angular/forms';

import { AppComponent } from './app.component';

@NgModule({
  declarations: [
    AppComponent
  ],
  imports: [
    BrowserModule,
    ReactiveFormsModule
  ],
  providers: [],
  bootstrap: [AppComponent]
})
export class AppModule { }

Import Bootstrap 4

Open src/index.html and add following line to <head> tag:

<!doctype html>
<html lang="en">
<head>
  ...
  <link href="//netdna.bootstrapcdn.com/bootstrap/4.5.2/css/bootstrap.min.css" rel="stylesheet" />
</head>
<body>
  <app-root></app-root>
</body>
</html>

Form Validation with Angular 11 Reactive Forms

The app component contains Form Validation example built with the @angular/forms version 11.

Open app/app.component.ts, we’re gonna import necessary library first:

import { Component, OnInit } from '@angular/core';
import { AbstractControl, FormBuilder, FormGroup, Validators } from '@angular/forms';
import Validation from './utils/validation';

We use Angular FormBuilder to create a FormGroup object (form property) which is then bound to the template <form> element (using the [formGroup] directive later).

Validators provides a set of built-in validators (required, minLength, maxLength…) that can be used by form controls.

A validator is a function that processes a FormControl or collection of controls and returns an error map or null (meaning validation has passed).

Validation is our custom class that provides custom validator function. I will explain it later.

export class AppComponent implements OnInit {
  form: FormGroup;
  submitted = false;

  constructor(private formBuilder: FormBuilder) {}

  ngOnInit(): void {
    this.form = this.formBuilder.group(
      {
        fullname: ['', Validators.required],
        username: [
          '',
          [
            Validators.required,
            Validators.minLength(6),
            Validators.maxLength(20)
          ]
        ],
        email: ['', [Validators.required, Validators.email]],
        password: [
          '',
          [
            Validators.required,
            Validators.minLength(6),
            Validators.maxLength(40)
          ]
        ],
        confirmPassword: ['', Validators.required],
        acceptTerms: [false, Validators.requiredTrue]
      },
      {
        validators: [Validation.match('password', 'confirmPassword')]
      }
    );
  }

  ...
}

We also have getter f to access form controls (form.controls) from the template. For example, we can get username field in the template using f.username instead of form.controls.username.

The submitted property helps us to check whether the form is submitted or not.

export class AppComponent implements OnInit {
  form: FormGroup;
  submitted = false;

  constructor(private formBuilder: FormBuilder) {}

  ngOnInit(): void {
    ...
  }

  get f(): { [key: string]: AbstractControl } {
    return this.form.controls;
  }

  onSubmit(): void {
    this.submitted = true;

    if (this.form.invalid) {
      return;
    }

    console.log(JSON.stringify(this.form.value, null, 2));
  }

  onReset(): void {
    this.submitted = false;
    this.form.reset();
  }
}

Angular 11 Form Validation template

Now we create the form with input fields and validation messages.

We bind to the FormGroup object (form) in the app component using [formGroup] directive. Form submit event will call onSubmit() handler above using event binding (ngSubmit).

Validation messages will display after form submission for the first time by submitted property.

app/app.component.html

<div class="register-form">
  <form [formGroup]="form" (ngSubmit)="onSubmit()">
    <div class="form-group">
      <label>Full Name</label>
      <input
        type="text"
        formControlName="fullname"
        class="form-control"
        [ngClass]="{ 'is-invalid': submitted && f.fullname.errors }"
      />
      <div *ngIf="submitted && f.fullname.errors" class="invalid-feedback">
        <div *ngIf="f.fullname.errors.required">Fullname is required</div>
      </div>
    </div>

    <div class="form-group">
      <label>Username</label>
      <input
        type="text"
        formControlName="username"
        class="form-control"
        [ngClass]="{ 'is-invalid': submitted && f.username.errors }"
      />
      <div *ngIf="submitted && f.username.errors" class="invalid-feedback">
        <div *ngIf="f.username.errors.required">Username is required</div>
        <div *ngIf="f.username.errors.minlength">
          Username must be at least 6 characters
        </div>
        <div *ngIf="f.username.errors.maxlength">
          Username must not exceed 20 characters
        </div>
      </div>
    </div>

    <div class="form-group">
      <label>Email</label>
      <input
        type="text"
        formControlName="email"
        class="form-control"
        [ngClass]="{ 'is-invalid': submitted && f.email.errors }"
      />
      <div *ngIf="submitted && f.email.errors" class="invalid-feedback">
        <div *ngIf="f.email.errors.required">Email is required</div>
        <div *ngIf="f.email.errors.email">Email is invalid</div>
      </div>
    </div>

    <div class="form-group">
      <label>Password</label>
      <input
        type="password"
        formControlName="password"
        class="form-control"
        [ngClass]="{ 'is-invalid': submitted && f.password.errors }"
      />
      <div *ngIf="submitted && f.password.errors" class="invalid-feedback">
        <div *ngIf="f.password.errors.required">Password is required</div>
        <div *ngIf="f.password.errors.minlength">
          Password must be at least 6 characters
        </div>
        <div *ngIf="f.password.errors.maxlength">
          Username must not exceed 40 characters
        </div>
      </div>
    </div>

    <div class="form-group">
      <label>Confirm Password</label>
      <input
        type="password"
        formControlName="confirmPassword"
        class="form-control"
        [ngClass]="{ 'is-invalid': submitted && f.confirmPassword.errors }"
      />
      <div
        *ngIf="submitted && f.confirmPassword.errors"
        class="invalid-feedback"
      >
        <div *ngIf="f.confirmPassword.errors.required">
          Confirm Password is required
        </div>
        <div *ngIf="f.confirmPassword.errors.matching">
          Confirm Password does not match
        </div>
      </div>
    </div>

    <div class="form-group form-check">
      <input
        type="checkbox"
        formControlName="acceptTerms"
        class="form-check-input"
        [ngClass]="{ 'is-invalid': submitted && f.acceptTerms.errors }"
      />
      <label for="acceptTerms" class="form-check-label"
        >I have read and agree to the Terms</label
      >
      <div *ngIf="submitted && f.acceptTerms.errors" class="invalid-feedback">
        Accept Terms is required
      </div>
    </div>

    <div class="form-group">
      <button type="submit" class="btn btn-primary">Register</button>
      <button
        type="button"
        (click)="onReset()"
        class="btn btn-warning float-right"
      >
        Reset
      </button>
    </div>
  </form>
</div>

Confirm Password validation in Angular 11

Now we will use Angular Custom Validator to implement password and confirm password validation..

– First, the validator returns null (meaning validation has passed) if there is any error on the control that we want to check (confirm password).
– Then, the validator checks that two fields match or not and set error on checking control if validation fails.

import { AbstractControl, ValidatorFn } from '@angular/forms';

export default class Validation {
  static match(controlName: string, checkControlName: string): ValidatorFn {
    return (controls: AbstractControl) => {
      const control = controls.get(controlName);
      const checkControl = controls.get(checkControlName);

      if (checkControl.errors && !checkControl.errors.matching) {
        return null;
      }

      if (control.value !== checkControl.value) {
        controls.get(checkControlName).setErrors({ matching: true });
        return { matching: true };
      } else {
        return null;
      }
    };
  }
}

Run Angular 11 Form Validation App

You can run our App with command: npm start.
If the process is successful, open Browser with Url: http://localhost:4200/ and check it.

Or run on Stackblitz:

Conclusion

Today we’ve built Angular 11 Form Validation example successfully with Reactive Forms Module & Bootstrap 4.

You can also use the Form Validation in following posts:
Angular 11 File upload example with progress bar
Angular 11 CRUD Application example with Web API
Angular 11 JWT Authentication example with Web Api

Happy learning! See you again.

Further Reading

Serverless with Firebase:
Angular 11 Firebase CRUD Realtime DB | AngularFireDatabase
Angular 11 Firestore CRUD example | AngularFireStore
Angular 11 File Upload Firebase Storage: Display/Delete Files example

Fullstack CRUD Application:
Angular + Node.js Express + MySQL example
Angular + Node.js Express + PostgreSQL example
Angular + Node.js Express + MongoDB example
Angular + Spring Boot + MySQL example
Angular + Spring Boot + PostgreSQL example
Angular + Spring Boot + MongoDB example
Angular + Django example
Angular + Django + MySQL example
Angular + Django + PostgreSQL example
Angular + Django + MongoDB example

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