Modules vs Standalone

Standalone Components (Modern - Default)

Standalone is the default and recommended approach for Angular 17+.

import { Component } from '@angular/core';
import { CommonModule } from '@angular/common';

@Component({
  selector: 'app-user',
  standalone: true,
  imports: [CommonModule],
  template: `<p>User component</p>`
})
export class UserComponent {}

Bootstrapping Standalone

// main.ts
import { bootstrapApplication } from '@angular/platform-browser';
import { provideHttpClient } from '@angular/common/http';
import { provideRouter } from '@angular/router';

bootstrapApplication(AppComponent, {
  providers: [
    provideHttpClient(),
    provideRouter(routes),
    UserService
  ]
});

Standalone App Component

import { Component } from '@angular/core';
import { RouterOutlet, RouterLink } from '@angular/router';
import { CommonModule } from '@angular/common';

@Component({
  selector: 'app-root',
  standalone: true,
  imports: [
    CommonModule,
    RouterOutlet,
    RouterLink,
    UserListComponent
  ],
  template: `
    <nav>
      <a routerLink="/">Home</a>
      <a routerLink="/users">Users</a>
    </nav>
    <router-outlet></router-outlet>
  `
})
export class AppComponent {}

Standalone Routes

import { Routes } from '@angular/router';

export const routes: Routes = [
  {
    path: '',
    loadComponent: () => import('./home/home.component')
      .then(m => m.HomeComponent)
  },
  {
    path: 'users',
    loadComponent: () => import('./users/user-list.component')
      .then(m => m.UserListComponent)
  },
  {
    path: 'admin',
    loadChildren: () => import('./admin/admin.routes')
      .then(m => m.ADMIN_ROUTES)
  }
];

Lazy Loading Standalone

// admin.routes.ts
import { Routes } from '@angular/router';

export const ADMIN_ROUTES: Routes = [
  {
    path: '',
    loadComponent: () => import('./admin-dashboard.component')
      .then(m => m.AdminDashboardComponent)
  },
  {
    path: 'users',
    loadComponent: () => import('./admin-users.component')
      .then(m => m.AdminUsersComponent)
  }
];

Mixing Modules and Standalone

// Import standalone component in NgModule
@NgModule({
  imports: [
    BrowserModule,
    UserComponent // Standalone component
  ],
  declarations: [AppComponent]
})
export class AppModule {}

// Import NgModule in standalone component
@Component({
  standalone: true,
  imports: [
    CommonModule,
    ReactiveFormsModule // NgModule
  ]
})
export class FormComponent {}

Providers in Standalone

// Component-level
@Component({
  standalone: true,
  providers: [UserService] // New instance per component
})
export class UserComponent {}

// Application-level
bootstrapApplication(AppComponent, {
  providers: [
    { provide: API_URL, useValue: 'https://api.example.com' },
    UserService // Singleton
  ]
});

// Service-level
@Injectable({ providedIn: 'root' })
export class UserService {}

Common Imports

// Always import these when needed
import { CommonModule } from '@angular/common'; // *ngIf, *ngFor, pipes
import { FormsModule } from '@angular/forms'; // ngModel
import { ReactiveFormsModule } from '@angular/forms'; // Reactive forms
import { RouterModule } from '@angular/router'; // routerLink, router-outlet
import { HttpClientModule } from '@angular/common/http'; // Legacy
// Or
import { provideHttpClient } from '@angular/common/http'; // Standalone

Migration Tips

From NgModule to Standalone:

1. Add standalone: true to @Component
2. Add imports: [] array
3. Import needed modules/components
4. Remove from NgModule declarations
5. Update routing to use loadComponent

Example:

// Before
@Component({
  selector: 'app-user'
})

@NgModule({
  declarations: [UserComponent]
})

// After
@Component({
  selector: 'app-user',
  standalone: true,
  imports: [CommonModule]
})

Benefits of Standalone

• Simpler - No NgModules needed
• Faster - Better tree-shaking
• Explicit - Clear dependencies
• Lazy loading - Component-level
• Less boilerplate
• Better DX - Easier to understand

NgModules (Legacy)

Only use NgModules for legacy applications or when maintaining existing code.

import { NgModule } from '@angular/core';
import { BrowserModule } from '@angular/platform-browser';

@NgModule({
  declarations: [AppComponent, UserComponent],
  imports: [BrowserModule],
  providers: [UserService],
  bootstrap: [AppComponent]
})
export class AppModule {}

When to Use Each

Use Standalone (Recommended)

• All new applications (Angular 17+)
• Component libraries
• Better tree-shaking and performance
• Simpler, more explicit dependencies

Use NgModules (Legacy only)

• Maintaining existing NgModule-based apps
• Gradual migration from old codebase

Best Practices

• Always use standalone for new Angular 17+ applications
• Use bootstrapApplication() for app initialization
• Use provideHttpClient() instead of HttpClientModule
• Import only what you need in each component
• Use loadComponent for lazy loading
• Keep imports array organized and minimal