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Angular 2/4 Pattern Validation Example

By Arvind Rai, December 19, 2017
This page will walk through Angular pattern validation example. Angular provides PatternValidator Directive that adds the pattern validator to any controls marked with the pattern attribute. We need to provide regex as attribute value. pattern attribute is bound to Validators.pattern. In our example we will perform pattern validation with formControl, ngModel, formControlName, FormGroup and FormBuilder.
Angular 4 uses novalidate attribute by default in its form element at run time and hence while submitting form, HTML 5 validation will not work. If we are using Angular 2, we need to write novalidate attribute in our form element to disable HTML 5 validation and use Angular form validation. Here in our example we will provide pattern validation for username, password, mobile number and email with Template-driven form as well as Reactive form. Now find the complete example step by step.

Technologies Used

Find the technologies being used in our example.
1. Angular 5.0.0
2. Angular CLI 1.5.4
3. TypeScript 2.4.2
4. Node.js 6.11.0
5. NPM 3.10.10

Project Structure

Find the project structure of our demo application.
my-app
|
|--src
|   |
|   |--app 
|   |   |
|   |   |--user.ts
|   |   |--user-service.ts
|   |   |--reactive-form.component.ts
|   |   |--reactive-form.component.html
|   |   |--template-driven-form.component.ts
|   |   |--template-driven-form.component.html
|   |   |
|   |   |--app.component.ts
|   |   |--app.module.ts 
|   | 
|   |--main.ts
|   |--index.html
|   |--styles.css
|
|--node_modules
|--package.json 

PatternValidator

PatternValidator is an Angular Directive. It ads pattern validator to any control that is using pattern attribute. The value of pattern will be a regex. According to given regex, validation will be performed. pattern attribute can be used with formControl, ngModel and formControlName. To work with FormGroup and FormBuilder we will get pattern from Validators by calling Validators.pattern. PatternValidator Directive has following selectors.
[pattern][formControlName]
[pattern][formControl]
[pattern][ngModel] 

Pattern Validation with formControl

We will perform pattern validation with formControl here. Suppose we have created an instance of FormControl for user name as following.
username = new FormControl(); 
In HTML template we will use Angular pattern attribute with regex in following way.
<input [formControl]="username" pattern="^[a-z0-9_-]{8,15}$"> 
We can bind component property with pattern using Angular property binding. Suppose we have following component property for regex to validate user name.
unamePattern = "^[a-z0-9_-]{8,15}$"; 
Use property binding as following.
<input [formControl]="username" [pattern]="unamePattern"> 
To display validation error message, find the code snippet.
<div *ngIf="username.errors?.pattern">
     User name not valid.
</div> 

Pattern Validation with ngModel

We will perform pattern validation with ngModel here. Suppose we have a regex to validate username as given below.
unamePattern = "^[a-z0-9_-]{8,15}$"; 
To perform validation with ngModel, we will use pattern attribute in following way.
<input name="username" [ngModel]="user.username" [pattern]="unamePattern" #uname="ngModel"> 
Now display validation error message.
<div *ngIf="uname.errors?.pattern"> 
   User name not valid.
</div> 

Pattern Validation with formControlName

We will perform pattern validation with formControlName here. To understand it we are creating a form with FormBuilder. We are also initializing a component property for regex.
unamePattern = "^[a-z0-9_-]{8,15}$";
userForm = this.formBuilder.group({
    username: '',
    ------
}) 
userForm is the instance of FormGroup. Now we can use pattern with formControlName as given below.
<input formControlName="username" [pattern]="unamePattern"> 
To access any control from FormGroup we will create getter for that control.
get username() {
     return this.userForm.get('username');
} 
Now display validation error message as following.
<div *ngIf="username.errors?.pattern">
     User name not valid.
</div> 

Validators.pattern with FormBuilder

We can use Validators.pattern for pattern validation while creating form either by FormBuilder or by FormGroup. Here we will provide code snippet for FormBuilder. Find the form for user created by FormBuilder and also find the sample regex.
unamePattern = "^[a-z0-9_-]{8,15}$";
userForm = this.formBuilder.group({
   username: ['', Validators.pattern(this.unamePattern)],
   ------
}) 
Look into the above code, while creating user name control, we are passing Validators.pattern. Our HTML code will be as follows.
<input formControlName="username"> 
To access form control, we will create a getter as following.
get username() {
     return this.userForm.get('username');
} 
Display validation error message as following.
<div *ngIf="username.errors?.pattern">
     User name not valid.
</div> 

Validators.pattern with FormGroup

We will provide pattern validation with FormGroup here. We will create a user form by using FormGroup. We will create a user name control using FormControl and pass Validators.pattern to it. We will also create a component property for regex.
unamePattern = "^[a-z0-9_-]{8,15}$";
userForm = new FormGroup({
   username: new FormControl('', Validators.pattern(this.unamePattern)),
   ------
}) 
Find the HTML code snippet.
<input formControlName="username"> 
To access form control, find the getter.
get username() {
     return this.userForm.get('username');
} 
Display validation error message as following.
<div *ngIf="username.errors?.pattern">
     User name not valid.
</div> 

Example-1: Pattern Validation using Reactive Form

user.ts
export class User {
    username: string;
    password: string;
    mobileNumber: string;
    email: string;
} 
reactive-form.component.ts
import { Component, OnInit } from '@angular/core';
import { FormControl, FormBuilder, Validators } from '@angular/forms';
import { UserService } from './user-service';
import { User } from './user';

@Component({
   selector: 'app-reactive',
   templateUrl: './reactive-form.component.html'
})
export class ReactiveFormComponent implements OnInit {
  unamePattern = "^[a-z0-9_-]{8,15}$";
  pwdPattern = "^(?=.*\d)(?=.*[a-z])(?=.*[A-Z])(?!.*\s).{6,12}$";
  mobnumPattern = "^((\\+91-?)|0)?[0-9]{10}$"; 
  emailPattern = "^[a-z0-9._%+-]+@[a-z0-9.-]+\.[a-z]{2,4}$";
  
  isValidFormSubmitted = null;
  
  userForm = this.formBuilder.group({
    username: ['', [Validators.required, Validators.pattern(this.unamePattern)]],
    password: ['', [Validators.required, Validators.pattern(this.pwdPattern)]],
    mobileNumber: ['', Validators.pattern(this.mobnumPattern)],
    email: ['', Validators.pattern(this.emailPattern)],
  });

  constructor(private formBuilder:FormBuilder, private userService: UserService) {
  }
  ngOnInit() {
  }
  onFormSubmit() {
     this.isValidFormSubmitted = false;
     if (this.userForm.invalid) {
        return;
     }
     this.isValidFormSubmitted = true;
     let user: User = this.userForm.value;
     this.userService.createUser(user);
     this.userForm.reset();
  }
  get username() {
     return this.userForm.get('username');
  }
  get password() {
     return this.userForm.get('password');
  }  
  get mobileNumber() {
     return this.userForm.get('mobileNumber');
  }    
  get email() {
     return this.userForm.get('email');
  }      
} 
reactive-form.component.html
<h3>Reactive Form</h3>
<p *ngIf="isValidFormSubmitted && userForm.pristine" [ngClass] = "'success'">
    Form submitted successfully.
</p>
<form [formGroup]="userForm" (ngSubmit)="onFormSubmit()">
 <table>
  <tr> 
	<td>User Name: </td>
	<td> 
		<input formControlName="username">
		<div *ngIf="username.errors && isValidFormSubmitted != null && !isValidFormSubmitted" [ngClass] = "'error'"> 
			<div *ngIf="username.errors.required">
				User name required.
			</div>  
			<div *ngIf="username.errors.pattern">
				User name not valid.
			</div> 
		</div>
	</td>
  </tr> 
  <tr> 
	<td>Password: </td>
	<td> 
		<input type="password" formControlName="password">
		<div *ngIf="password.errors && isValidFormSubmitted != null && !isValidFormSubmitted" [ngClass] = "'error'"> 
			<div *ngIf="password.errors.required">
				Password required.
			</div>  
			<div *ngIf="password.errors.pattern">
				Password not valid.
			</div> 
		</div>		   
	</td>
  </tr> 	 
  <tr>
	<td>Mobile Number: </td>
	<td> 
		<input formControlName="mobileNumber">
		<div *ngIf="mobileNumber.errors && isValidFormSubmitted != null && !isValidFormSubmitted" [ngClass] = "'error'"> 
			<div *ngIf="mobileNumber.errors.pattern">
				Mobile number not valid.
			</div> 
		</div>		   
	</td>
  </tr> 	 	 
  <tr>
	<td>Email: </td>
	<td> 
		<input formControlName="email">
		<div *ngIf="email.errors && isValidFormSubmitted != null && !isValidFormSubmitted" [ngClass] = "'error'"> 
			<div *ngIf="email.errors.pattern">
				Email not valid.
			</div> 
		</div>		   
	</td>
  </tr>
  <tr> 	  
	<td colspan="2">
		<button>Submit</button>
	</td>
  </tr>	   
 </table>  
</form> 
user-service.ts
import { Injectable } from '@angular/core';
import { User } from './user';

@Injectable()
export class UserService {
   createUser(user: User) {
     console.log('User Name: ' + user.username);
     console.log('Password: ' + user.password);
     console.log('Mobile Number: ' + user.mobileNumber);
     console.log('Email: ' + user.email);
   }
} 

Example-2: Pattern Validation using Template-driven Form

template-driven-form.component.ts
import { Component, OnInit } from '@angular/core';
import { NgForm } from '@angular/forms';
import { UserService } from './user-service';
import { User } from './user';

@Component({
   selector: 'app-template',
   templateUrl: './template-driven-form.component.html'
})
export class TemplateDrivenFormComponent implements OnInit {
  unamePattern = "^[a-z0-9_-]{8,15}$";
  pwdPattern = "^(?=.*\d)(?=.*[a-z])(?=.*[A-Z])(?!.*\s).{6,12}$";
  mobnumPattern = "^((\\+91-?)|0)?[0-9]{10}$"; 
  emailPattern = "^[a-z0-9._%+-]+@[a-z0-9.-]+\.[a-z]{2,4}$";

  isValidFormSubmitted = false;
  validateEmail = true;
  user = new User();

  constructor(private userService: UserService) {
  }
  ngOnInit() {
  }
  onFormSubmit(form: NgForm) {
     this.isValidFormSubmitted = false;
     if (form.invalid) {
        return;
     }
     this.isValidFormSubmitted = true;
     this.user = form.value;
     this.userService.createUser(this.user);
     this.user = new User();
     form.resetForm();
  }
} 
template-driven-form.component.html
<h3>Template-driven Form</h3>
<p *ngIf="isValidFormSubmitted" [ngClass] = "'success'">
    Form submitted successfully.
</p>
<form #userForm="ngForm" (ngSubmit)="onFormSubmit(userForm)">
 <table>
  <tr> 
	<td>User Name:</td>
	<td> 
		<input name="username" [ngModel]="user.username" required [pattern]="unamePattern" #uname="ngModel">
		<div *ngIf="uname.errors && userForm.submitted && !isValidFormSubmitted" [ngClass] = "'error'"> 
			<div *ngIf="uname.errors.required"> 
				User name required.
			</div>						
			<div *ngIf="uname.errors.pattern"> 
				User name not valid.
			</div>	
		</div>
	</td>
  </tr> 
  <tr> 
	<td>Password:</td>
	<td> 
		<input name="password" type="password" [ngModel]="user.password" required [pattern]="pwdPattern" #pwd="ngModel">
		<div *ngIf="pwd.errors && userForm.submitted && !isValidFormSubmitted" [ngClass] = "'error'"> 
			<div *ngIf="pwd.errors.required"> 
				Password required.
			</div>
			<div *ngIf="pwd.errors.pattern"> 
				Password not valid.
			</div>	
		</div>
	</td>
  </tr> 	 
  <tr> 
	<td>Mobile Number:</td>
	<td> 
		<input name="mobileNumber" [ngModel]="user.mobileNumber" [pattern]="mobnumPattern" #mobnum="ngModel">
		<div *ngIf="mobnum.errors && userForm.submitted && !isValidFormSubmitted" [ngClass] = "'error'"> 
			<div *ngIf="mobnum.errors.pattern"> 
				Mobile number not valid.
			</div>	
		</div>
	</td>
  </tr> 	
  <tr> 
	<td>Email:</td>
	<td> 
		<input name="email" [ngModel]="user.email" [pattern]="emailPattern" #userEmail="ngModel">
		<div *ngIf="userEmail.errors && userForm.submitted && !isValidFormSubmitted" [ngClass] = "'error'"> 
			<div *ngIf="userEmail.errors.pattern"> 
				User name not valid.
			</div>	
		</div>
	</td>
  </tr> 		  	 
  <tr> 	  
	<td colspan="2">
		<button>Submit</button>
	</td>
  </tr>	   
 </table>  
</form> 
app.component.ts
import { Component } from '@angular/core';

@Component({
   selector: 'app-root',
   template: `
		<app-reactive></app-reactive>
		<app-template></app-template>				
             `
})
export class AppComponent {
} 
app.module.ts
import { NgModule } from '@angular/core';
import { BrowserModule } from '@angular/platform-browser';
import { FormsModule, ReactiveFormsModule } from '@angular/forms';
import { AppComponent } from './app.component';
import { ReactiveFormComponent } from './reactive-form.component';
import { TemplateDrivenFormComponent } from './template-driven-form.component';
import { UserService } from './user-service';

@NgModule({
  imports: [
      BrowserModule,
      FormsModule,
      ReactiveFormsModule
  ],
  declarations: [
      AppComponent,
      ReactiveFormComponent,
      TemplateDrivenFormComponent	  
  ],
  providers: [
      UserService
  ],
  bootstrap: [
      AppComponent
  ]
})
export class AppModule { } 
styles.css
table {
    border-collapse: collapse;
}
table, th, td {
    border: 1px solid black;
}
.error {
    color: red;
}
.success {
    color: green;
}  

Run Application

To run the application, find following steps.
1. Download source code using download link given below on this page.
2. Use downloaded src in your Angular CLI application. To install Angular CLI, find the link.
3. Run ng serve using command prompt.
4. Now access the URL http://localhost:4200
When we enter invalid data and click on submit button, we will get following output.
Angular 2/4 Pattern Validation Example
Find a sample input for successful validation.
User Name: concretepage
Password: x2z@dG1
Mobile Number: 9812703058
Email: mahesh@gmail.com 

References

PatternValidator
Angular QuickStart

Download Source Code

POSTED BY
ARVIND RAI
ARVIND RAI
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