How to validate not allowed whitespace in Angular?

Hi Dev,

Here, i will show you angular reactive form not allow whitespace in validator. how to create custom validation for not allow white space in angular app. you can simply create validation for not allowing white space in angular 8 app.

Actually, few days ago i was working on my reactive form and i need to add custom validation for not allow white space. i thought i will use something if condition or anything else. but i found way to create custom validation for rules for this. so i created very simple way for no space allow to input field in angular application.

We will create new custom validator for not contain space on input field. we will not allow space on username.

Step 1: Install Angular App

Here, in this step you need to create new ng app for this demo. if you have already created then don't create new angular 8 app.

ng new my-custom-val-app

Step 2: Import FormsModule

If you want to create form in angular app then you need to import FormsModule from @angular/forms library. so let's add following code to app.module.ts file.

src/app/app.module.ts

import { BrowserModule } from '@angular/platform-browser';
import { NgModule } from '@angular/core';
import { FormsModule, ReactiveFormsModule } from '@angular/forms';
   
import { AppComponent } from './app.component';
   
@NgModule({
  declarations: [
    AppComponent
  ],
  imports: [
    BrowserModule,
    FormsModule,
    ReactiveFormsModule
  ],
  providers: [],
  bootstrap: [AppComponent]
})
export class AppModule { }

Step 3: Form with ngModel

In this step, we will write code of html form with ngModel. so add following code to app.component.html file.

I used bootstrap class on this form. if you want to add than then follow this link too: Install Boorstrap 4 to Angular 8.

src/app/app.component.html

<h1>How to Create Custom Validators in Angular 8 - ItSolutionStuff.com</h1>
    
<form [formGroup]="form" (ngSubmit)="submit()">
   
    <div class="form-group">
        <label for="username">Username</label>
        <input 
            formControlName="username"
            id="username" 
            type="text" 
            class="form-control">
        <div *ngIf="f.username.touched && f.username.invalid" class="alert alert-danger">
            <div *ngIf="f.username.errors.required">Username is required.</div>
            <div *ngIf="f.username.errors.minlength">Username should be 3 character.</div>
            <div *ngIf="f.username.errors.cannotContainSpace">Username can not contain space.</div>
        </div>
    </div>
     
    <div class="form-group">
        <label for="password">Password</label>
        <input 
            formControlName="password"
            id="password" 
            type="password" 
            class="form-control">
        <div *ngIf="f.password.touched && f.password.invalid" class="alert alert-danger">
            <div *ngIf="f.password.errors.required">Password is required.</div>
        </div>
    </div>
    
    <button class="btn btn-primary" type="submit">Submit</button>
</form>

Step 4: updated Ts File

In ts file. we will write submit() and get all input fields values. so let's add following code to app.component.ts file.

src/app/app.component.ts

import { Component } from '@angular/core';
import { FormGroup, FormControl, Validators} from '@angular/forms';
import { UsernameValidator } from './username.validator';
  
@Component({
  selector: 'app-root',
  templateUrl: './app.component.html',
  styleUrls: ['./app.component.css']
})
export class AppComponent {
  form = new FormGroup({
    username: new FormControl('', [Validators.required, Validators.minLength(3), UsernameValidator.cannotContainSpace]),
    password: new FormControl('', Validators.required)
  });
   
  get f(){
    return this.form.controls;
  }
    
  submit(){
    console.log(this.form.value);
  }
}

Step 5: Create Custom Validation File

You need to create custom 'username.validator.ts' file and write code as bellow:

src/app/username.validator.ts

import { AbstractControl, ValidationErrors } from '@angular/forms';
  
export class UsernameValidator {
    static cannotContainSpace(control: AbstractControl) : ValidationErrors | null {
        if((control.value as string).indexOf(' ') >= 0){
            return {cannotContainSpace: true}
        }
  
        return null;
    }
}

Now you can run your application using following command:

ng serve

I hope it can help you...