Angular 6中的字母数字字符串验证

import { Validators } from '@angular/forms';

import { Component } from '@angular/core';
import { FormGroup, FormBuilder } from '@angular/forms';

@Component({
  selector: 'app-my-form',
  templateUrl: './my-form.component.html',
})
export class MyFormComponent {
  myForm: FormGroup;

  constructor(private fb: FormBuilder) {
    this.myForm = this.fb.group({
      alphanumeric: ['', [Validators.required, Validators.pattern(/^[a-zA-Z0-9]+$/)]]
    });
  }
}

<input type="text" formControlName="alphanumeric">
<div *ngIf="myForm.controls.alphanumeric.errors">
  <div *ngIf="myForm.controls.alphanumeric.errors.required">该字段不能为空</div>
  <div *ngIf="myForm.controls.alphanumeric.errors.pattern">该字段只能包含字母和数字</div>
</div>