Check out example codes for "angular numbers only directive". It will help you in understanding the concepts better.

Code Example 1

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

@Directive({
  selector: 'input[type=number], input[numbersOnly]'
})
export class NumbersOnlyInputDirective {

  constructor(private elRef: ElementRef) { }

  @HostListener('input', ['$event']) onInputChange(event) {
    const initalValue = this.elRef.nativeElement.value;
    this.elRef.nativeElement.value = initalValue.replace(/[^0-9]*/g, '');
    if ( initalValue !== this.elRef.nativeElement.value) {
      event.stopPropagation();
    }
  }

}

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