Angular11芯片防止用户输入错误的值

<form #form="ngForm" (ngSubmit)="onSubmit(form.value)">
  <input type="text" name="username" [(ngModel)]="user.username" required minlength="3" maxlength="10">
  <div *ngIf="form.controls['username'].errors?.required">Username is required.</div>
  <div *ngIf="form.controls['username'].errors?.minlength">Username must be at least 3 characters long.</div>
  <button type="submit">Submit</button>
</form>

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

@Component({
  selector: 'app-user-form',
  templateUrl: './user-form.component.html',
  styleUrls: ['./user-form.component.css']
})
export class UserFormComponent {
  userForm: FormGroup;

  constructor(private fb: FormBuilder) {
    this.userForm = this.fb.group({
      username: ['', [Validators.required, Validators.minLength(3), Validators.maxLength(10)]]
    });
  }

  onSubmit() {
    if (this.userForm.valid) {
      console.log(this.userForm.value);
    }
  }
}

<form [formGroup]="userForm" (ngSubmit)="onSubmit()">
  <input type="text" formControlName="username">
  <div *ngIf="userForm.get('username').errors?.required">Username is required.</div>
  <div *ngIf="userForm.get('username').errors?.minlength">Username must be at least 3 characters long.</div>
  <button type="submit" [disabled]="!userForm.valid">Submit</button>
</form>

onSubmit() {
  if (this.userForm.valid) {
    console.log(this.userForm.value);
  } else {
    console.log('Form is invalid');
  }
}

function customValidator(control) {
  if (control.value === 'invalid') {
    return { invalidValue: true };
  }
  return null;
}

this.userForm = this.fb.group({
  username: ['', [Validators.required, customValidator]]
});