Directiva para formatear RUT en Ionic2

app.module.ts

@NgModule({
    declarations: [
        //...
        IonRutDirective
        //...
    ]
})

home.html

<form>
    <ion-input type="text" placeholder="Escriba su RUT aquí..." ion-rut>
</form>

ion-rut.ts

import {Directive, ElementRef, HostListener, Input} from '@angular/core';

@Directive({
    selector: '[ion-rut]',
    host : {
        '(focus)' : 'onFocus',
        '(blur)' : 'onBlur'
    }
})
export class IonRutDirective {
    @Input() name : string;
    @Input() value : string;

    constructor(public element : ElementRef) {}

    public validate (full:any) {
        if (typeof full == "number") full = (<number>full).toString();
        else if (typeof full !== "string") full = "";
        full = full.replace(/([^0-9kK\-]+)/g, '');
        if (!/^[0-9]+[-|‐]{1}[0-9k]{1}$/.test( full )) return false;
        let tmp 	= full.split('-');
        let dv:Function = (T:any) => {
            let M=0,S=1;
            for(;T;T=Math.floor(T/10)) S=(S+T%10*(9-M++%6))%11;
            return S?S-1:'k';
        };
        return (dv(tmp[0]) == tmp[1]);
    }

    public format (value:string) {
        value = typeof value === 'string' ? value.replace(/[^0-9kK]+/g, '').toUpperCase() : '';
        if (value.length <= 1) return value;
        let result: string = `${value.slice(-4, -1)}-${value.substr(value.length - 1)}`;
        for (let i: number = 4; i < value.length; i += 3) result = `${value.slice(-3 - i, -i)}.${result}`;
        return result;
    }

    public updateValidity () {
        if (!this.validate(this.element.nativeElement.firstElementChild.value)) {
            this.element.nativeElement.classList.add('ng-invalid');
            this.element.nativeElement.firstElementChild.classList.add('ng-invalid');
        }
        else {
            this.element.nativeElement.classList.remove('ng-invalid');
            this.element.nativeElement.firstElementChild.classList.remove('ng-invalid');
        }
    }

    @HostListener('blur') onBlur () {
        let element = this.element.nativeElement.firstElementChild;
        this.updateValidity();
        element.value = this.format(element.value);
    }

    @HostListener('focus') public onFocus () {
        let element = this.element.nativeElement.firstElementChild;
        this.updateValidity();
        element.value = this.format(element.value);
    }

    @HostListener('input') public onInput () {
        let element = this.element.nativeElement.firstElementChild;
        this.updateValidity();
        element.value = this.format(element.value);
    }
}