Mask for an Input to allow phone numbers?

Angular5 and 6:

angular 5 and 6 recommended way is to use @HostBindings and @HostListeners instead of the host property

remove host and add @HostListener

 @HostListener('ngModelChange', ['$event'])
  onModelChange(event) {
    this.onInputChange(event, false);
  }

  @HostListener('keydown.backspace', ['$event'])
  keydownBackspace(event) {
    this.onInputChange(event.target.value, true);
  }

Working Online stackblitz Link: https://angular6-phone-mask.stackblitz.io

Stackblitz Code example: https://stackblitz.com/edit/angular6-phone-mask

Official documentation link https://angular.io/guide/attribute-directives#respond-to-user-initiated-events

Angular2 and 4:

Plunker >= RC.5

original

One way you could do it is using a directive that injects NgControl and manipulates the value

(for details see inline comments)

@Directive({
  selector: '[ngModel][phone]',
  host: {
    '(ngModelChange)': 'onInputChange($event)',
    '(keydown.backspace)': 'onInputChange($event.target.value, true)'
  }
})
export class PhoneMask {
  constructor(public model: NgControl) {}

  onInputChange(event, backspace) {
    // remove all mask characters (keep only numeric)
    var newVal = event.replace(/\D/g, '');
    // special handling of backspace necessary otherwise
    // deleting of non-numeric characters is not recognized
    // this laves room for improvement for example if you delete in the 
    // middle of the string
    if (backspace) {
      newVal = newVal.substring(0, newVal.length - 1);
    } 

    // don't show braces for empty value
    if (newVal.length == 0) {
      newVal = '';
    } 
    // don't show braces for empty groups at the end
    else if (newVal.length <= 3) {
      newVal = newVal.replace(/^(\d{0,3})/, '($1)');
    } else if (newVal.length <= 6) {
      newVal = newVal.replace(/^(\d{0,3})(\d{0,3})/, '($1) ($2)');
    } else {
      newVal = newVal.replace(/^(\d{0,3})(\d{0,3})(.*)/, '($1) ($2)-$3');
    }
    // set the new value
    this.model.valueAccessor.writeValue(newVal);       
  }
}

@Component({
  selector: 'my-app',
  providers: [],
  template: `
  <form [ngFormModel]="form">
    <input type="text" phone [(ngModel)]="data" ngControl="phone"> 
  </form>
  `,
  directives: [PhoneMask]
})
export class App {
  constructor(fb: FormBuilder) {
    this.form = fb.group({
      phone: ['']
    })
  }
}

Plunker example <= RC.5