如何在Angular 6中编写保护程序以防止用户丢失表单数据？

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

@Component({
  selector: 'app-form',
  template: `
    <form [formGroup]="myForm">
      <input formControlName="name" placeholder="Name">
      <input formControlName="email" placeholder="Email">
    </form>
  `
})
export class FormComponent {
  myForm: FormGroup;

  constructor() {
    this.myForm = new FormGroup({
      name: new FormControl(''),
      email: new FormControl('')
    });
  }
}

import { Injectable } from '@angular/core';
import { CanDeactivate } from '@angular/router';
import { Observable } from 'rxjs';
import { FormComponent } from './form.component';

@Injectable()
export class FormGuard implements CanDeactivate<FormComponent> {
  canDeactivate(component: FormComponent): Observable<boolean> | boolean {
    if (component.myForm.dirty) {
      return confirm('Are you sure you want to leave this page?');
    }
    return true;
  }
}

import { NgModule } from '@angular/core';
import { Routes, RouterModule } from '@angular/router';
import { FormComponent } from './form.component';
import { FormGuard } from './form.guard';

const routes: Routes = [
  {
    path: 'form',
    component: FormComponent,
    canDeactivate: [FormGuard]
  }
];

@NgModule({
  imports: [RouterModule.forRoot(routes)],
  exports: [RouterModule],
  providers: [FormGuard]
})
export class AppRoutingModule { }