我有这个登记表。我试图验证它，但徒劳的。输入保存在我的数据库中，尽管他们是空的我想有这些验证：

• 所有输入都是必需的
• 电子邮件地址应有效
• 名称只能由字母组成
• 密码应至少包含8个字符，至少包含1个大写字母、1个小写字母和1个数字

我想在每一个无效输入下都有一个消息。（例如在<div id="na"></div>中）。请问我该怎么做？
HTML文件

<h2 class="text-center">Inscription</h2>
<div class="row">
<div class="col-md-3">
</div>
<div class="col-md-6 col-md-offset-3">
<div class="jumbotron">
<form [formGroup]="angForm" (ngSubmit)="postdata(angForm)" autocomplete="off">
<div class="form-group mb-3">
<label for="name">Nom</label>
<input type="text" name="name" formControlName="name" autocomplete="off" id="name" 
class="form-control input-sm" placeholder="Nom">
</div>
<div id="na"></div>
<div class="form-group mb-3">
<label for="email">Email</label>
<input type="email" name="email" formControlName="email" autocomplete="off" id="email" 
class="form-control input-sm" placeholder="Email">
</div>
<div id="mail"></div>
<div class="form-group mb-3">
<label for="Password">Mot de passe</label>
<input type="password" name="Password" formControlName="password" autocomplete="off" 
id="password" class="form-control input-sm" placeholder="Mot de passe">
</div>
<div id="pwd"></div>
<button type="sumit" class="btn btn-success">Enregistrer</button>
</form>
</div>
</div>
<div class="col-md-3">
</div>
</div>

类型脚本文件

import { Component, OnInit } from '@angular/core';
import { FormGroup, FormControl, FormBuilder, Validators, NgForm } from '@angular/forms';
import { first } from 'rxjs/operators';
import { Router } from '@angular/router';
import { ApiService } from '../api.service';
@Component({
selector: 'app-inscription',
templateUrl: './inscription.component.html',
styleUrls: ['./inscription.component.css']
})
export class InscriptionComponent implements OnInit {
angForm: FormGroup;
constructor(private fb: FormBuilder,private dataService: ApiService,private router:Router) {
this.angForm = this.fb.group({
email: [],
password: [],
name: [],
mobile: []
});
}
ngOnInit() {
}
postdata(angForm1:any){this.dataService.userregistration(angForm1.value.name,angForm1.value.email,angForm1.value.password)
.pipe(first())
.subscribe(
data => {
this.router.navigate(['login']);

},
error => {
});
}
 get email() { return this.angForm.get('email'); }
 get password() { return this.angForm.get('password'); }
 get name() { return this.angForm.get('name'); }
 }

先谢了