防止在移动设备Angular指令中键入特殊字符

Question

我有以下代码，可防止在浏览器应用程序中键入特殊字符。但是在移动用户中，其键盘有所不同，可以直接输入特殊字符。我该如何预防？

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

@Directive({
  selector: '[appNumeric]'
})
export class NumericDirective {

  constructor(private elemRef: ElementRef) { }

  @HostListener('keydown', ['$event']) onKeyDown(event) {
    const e = <KeyboardEvent>event;

    const keyCode = e.charCode || e.keyCode;

    const allowedKeys = [46, 8, 9, 27, 13];

    if (allowedKeys.indexOf(keyCode) !== -1 ||
      // Allow: Ctrl+A
      (keyCode === 65 && e.ctrlKey === true) ||
      // Allow: Ctrl+C
      (keyCode === 67 && e.ctrlKey === true) ||
      // Allow: Ctrl+X
      (keyCode === 88 && e.ctrlKey === true) ||
      // Allow: home, end, left, right
      (keyCode >= 35 && keyCode <= 39)) {
      // let it happen, don't do anything
      return;
    }
    // Ensure that it is a number and stop the keypress
    if ((e.shiftKey || (keyCode < 48 || keyCode > 57)) && (keyCode < 96 || keyCode > 105)) {
      e.preventDefault();
    }
  }
}