for tyler

numberfilterdirective.ts

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

@Directive({
  selector: '[appNumberFilter]'
})
export class NumberFilterDirective {
  invalidChars = [
    '-',
    '+',
    'e',
  ];
  constructor(private elementRef: ElementRef) { }

  @HostListener('keydown', ['$event']) onKeyDown(evt: KeyboardEvent): void {
    if (this.invalidChars.includes(evt.key)) {
      evt.preventDefault();
    }
  }
}