Directive - Soluction for Mask input in ionic/angular 4

ion-mask-input.html

<ion-input type="tel" pattern="\d*" placeholder="(xxx) xxx-xxxx" mask="(***) ***-****" [(ngModel)]="phone" name="phone"></ion-input>

ion-mask-input.ts

import { Directive, Attribute } from '@angular/core';
import { NgModel } from '@angular/forms';

@Directive({
    selector: '[mask]',
    host: { '(keyup)': 'onInputChange($event)' },
    providers: [NgModel]
})

export class InputMask {

    public pattern: string;

    constructor(public model: NgModel, @Attribute('mask') pattern: string) {
        this.pattern = pattern;
    }

    onInputChange(event) {
        let value = event.target.value,
            pattern = this.pattern;

        if (event.keyIdentifier === 'U+0008' || event.keyCode === 8 || event.key === 'Backspace') {
            if (value.length) {
                while (pattern[value.length] && pattern[value.length] !== '*') {
                    value = value.substring(0, value.length - 1);
                }
                // remove toda a formatação principal para restaurar o marcador de posição
                if (pattern.substring(0, value.length).indexOf('*') < 0) {
                    value = value.substring(0, value.length - 1);
                }
            }
        } else {
            let maskIndex = value.length,
                formatted = '';
            if (value.length === 1 && value !== pattern[0]) {
                // aplicando a formatação principal
                maskIndex = 0;
                while (maskIndex < pattern.length && pattern[maskIndex] !== '*') {
                    formatted += pattern[maskIndex];
                    maskIndex++;
                }
            }
            formatted += value;
            if (maskIndex < pattern.length) {
                // aplicando formatação final
                while (pattern[maskIndex] !== '*') {
                    formatted += pattern[maskIndex];
                    maskIndex++;
                }
            }
            value = formatted;
        }
        this.model.update.emit(value);
    }

}