directive.ts

import * as $ from 'jquery';
import 'jquery-mask-plugin/dist/jquery.mask';

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

@Directive({
  selector: '[appMaskNumber]'
})
export class MaskNumberDirective {

  constructor(private elementRef: ElementRef) {
    this.applyMask();
  }

  applyMask(){
    const nativeElement = this.elementRef.nativeElement; //DOM
    $(nativeElement).find('input').mask('#.##0,00', {reverse: true}); //ion-input ->input
  }
}

<ion-input appMaskNumber>