Angular reactive窗体自定义验证

import { AbstractControl, ValidatorFn } from '@angular/forms';

export function numberValidator(): ValidatorFn {
  return (control: AbstractControl): { [key: string]: any } | null => {
    const value = control.value;
    if (isNaN(value)) {
      return { 'number': true };
    }
    return null;
  };
}

import { Component } from '@angular/core';
import { FormBuilder, Validators } from '@angular/forms';
import { numberValidator } from './validators';

@Component({
  selector: 'app-form',
  template: `
    <form [formGroup]="myForm">
      <input formControlName="myField">
      <div *ngIf="myForm.get('myField').errors?.number">
        Please enter a valid number.
      </div>
    </form>
  `,
})
export class FormComponent {
  myForm = this.fb.group({
    myField: ['', [Validators.required, numberValidator()]]
  });

  constructor(private fb: FormBuilder) {}
}