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Reactive forms validation in Angular 17 | Custom validation in reactive form | Angular 17 directives

First, we must import to NgForm, FormsModule, ReactiveFormsModule, and CommonModule which will help us validate the Reactive forms in Angular 17.

import { CommonModule } from '@angular/common';

import { NgForm,FormsModule, ReactiveFormsModule } from '@angular/forms';

 

After that imports in the Component,

imports: [RouterOutlet, FormsModule, ReactiveFormsModule, and CommonModule]

 

See the example code for app.component.ts,

import { CommonModule } from '@angular/common';

import { Component } from '@angular/core';

import { NgForm, FormsModule, ReactiveFormsModule } from '@angular/forms';

import { RouterOutlet } from '@angular/router';

 

@Component({

  selector: 'app-root',

  standalone: true,

  imports: [RouterOutlet, FormsModule, ReactiveFormsModule, CommonModule],

  templateUrl: './app.component.html',

  styleUrl: './app.component.css'

})

export class AppComponent {

    title = 'Reactive forms validation in Angular 17';

 

    form = {

      fullname: '',

      username: '',

      email: '',

      password: '',

      acceptTerms: false,

    };

 

    onSubmit(): void {

      console.log(JSON.stringify(this.form));

    }

 

    onReset(form: NgForm): void {

        form.resetForm();

    }

}

 

See the example code for app.component.html,

<main class="main">

  <div class="content">

    <div class="left-side">  

      <h4>Angular 17 Template Driven Form Validation example</h4>

      <hr>

     

      <div class="register-form">

        <form

          name="form"

          #f="ngForm"

          (ngSubmit)="f.form.valid && onSubmit()"

          novalidate      

         >

       

          <div class="form-group">

            <label>Full Name</label>

            <input

              type="text"

              class="form-control"

              name="fullname"

              [(ngModel)]="form.fullname"

              required

              #fullname="ngModel"

              [ngClass]="{ 'is-invalid': f.submitted && fullname.errors }"

            />

            @if (f.submitted && fullname.errors) {

              <div class="invalid-feedback">

                @if (fullname.errors['required']) {

                <div>Full name is required</div>

                }

              </div>

            }

          </div>

     

          <div class="form-group">

            <label>Username</label>

            <input

              type="text"

              class="form-control"

              name="username"

              [(ngModel)]="form.username"

              required

              minlength="6"

              maxlength="20"

              #username="ngModel"

              [ngClass]="{ 'is-invalid': f.submitted && username.errors }"

            />

            @if (f.submitted && username.errors ){

              <div class="invalid-feedback">

                @if (username.errors['required']) {

                <div>Username is required</div>

                }

                @if (username.errors['minlength']) {

                <div>Username must be at least 6 characters</div>

                }

                @if (username.errors['maxlength']) {

                <div>Username must be at most 20 characters</div>

                }

              </div>

            }

          </div>

     

          <div class="form-group">

            <label>Email</label>

            <input

              type="email"

              class="form-control"

              name="email"

              [(ngModel)]="form.email"

              required

              email

              #email="ngModel"

              [ngClass]="{ 'is-invalid': f.submitted && email.errors }"

            />

            @if (f.submitted && email.errors) {

              <div class="invalid-feedback">

                @if (email.errors['required']) {

                <div>Email is required</div>

                }

                @if (email.errors['email']) {

                <div>Email is invalid</div>

                }

              </div>

            }

          </div>

     

          <div class="form-group">

            <label>Password</label>

            <input

              type="password"

              class="form-control"

              name="password"

              [(ngModel)]="form.password"

              required

              minlength="6"

              maxlength="40"

              #password="ngModel"

              [ngClass]="{ 'is-invalid': f.submitted && password.errors }"

            />

            @if (f.submitted && password.errors) {

              <div class="invalid-feedback">

                  @if (password.errors['required']) {

                  <div>Password is required</div>

                  }

                  @if (password.errors['minlength']) {

                  <div>Password must be at least 6 characters</div>

                  }

                  @if (password.errors['maxlength']) {

                  <div>Username must not exceed 40 characters</div>

                  }

              </div>

            }

          </div>

     

          <div class="form-group form-check">

            <input

              type="checkbox"

              class="form-control"

              name="acceptTerms"

              [(ngModel)]="form.acceptTerms"

              class="form-check-input"

              required

              #acceptTerms="ngModel"

              [ngClass]="{ 'is-invalid': f.submitted && acceptTerms.errors }"

            />

            <label for="acceptTerms" class="form-check-label">

              I have read and agree to the Terms

            </label>

              @if (f.submitted && acceptTerms.errors) {

              <div class="invalid-feedback">Accept Terms is required</div>

              }

          </div>

          <hr>

          <div class="form-group">

            <button type="submit" class="btn btn-primary">Register</button>

            <button

              type="button"

              (click)="onReset(f)"

              class="btn btn-warning float-right"

            >

              Reset

            </button>

          </div>

        </form>

      </div>

     

    </div>

  </div>

</main>

 

See the YouTube video on Reactive forms validation:- https://youtu.be/rAYqQtIPTFE

Download source code from Github:- https://github.com/anilsingh581/Angular-17-reactive-Form-Validation



By Anil Singh | Rating of this article (*****)

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