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What are Standalone Components in Angular?
Standalone components were introduced in Angular 14 to simplify the development process by reducing the need for the traditional NgModules (the module system that Angular uses to organize an application). A Standalone Component is essentially a component that can operate independently without being declared in any Angular module (@NgModule).
Before the introduction of standalone components, every component, directive, and pipe had to be part of an Angular module, which could become cumbersome. Standalone components allow you to:
- Create components, directives, and pipes that don't need an Angular module.
- Easily import required modules directly into the component.
How to Use Standalone Components
You can create and use a standalone component by adding the standalone: true flag to the component’s decorator. This flag tells Angular that this component is independent and does not require an NgModule for it to be functional.
Example:
1. Creating a Standalone Component
import { Component } from '@angular/core';
import { CommonModule } from '@angular/common'; // Import CommonModule (for common Angular functionality)
@Component({
selector: 'app-standalone',
template: `<h1>Hello from Standalone Component!</h1>`,
standalone: true,
imports: [CommonModule] // You can import necessary modules directly here
})
export class StandaloneComponent {}
2. Using the Standalone Component
To use this standalone component in your application, simply import it where it’s needed, just like you would with any other component.
For example, in another component (standalone or part of a module)
import { Component } from '@angular/core';
import { StandaloneComponent } from './standalone.component';
@Component({
selector: 'app-root',
template: ``,
standalone: true,
imports: [StandaloneComponent] // Import the standalone component directly
})
export class AppComponent {}
3. Bootstrapping the Standalone Component in main.ts
If you’re bootstrapping your application with a standalone component, you can do it in main.ts directly
import { platformBrowserDynamic } from '@angular/platform-browser-dynamic';
import { StandaloneComponent } from './app/standalone.component';
platformBrowserDynamic().bootstrapModule(StandaloneComponent)
.catch(err => console.error(err));
When to Use Standalone Components
Standalone components are especially useful in the following scenarios
- Simplified Modularization: Standalone components are ideal for smaller applications or micro-frontends where you don’t want to deal with the complexity of Angular Modules (NgModules).
- Reusability: If you're building libraries or shareable components, standalone components make it easier to distribute them without requiring a module wrapper.
- Isolated Development: When developing isolated features or experimental components, standalone components reduce boilerplate code related to modules.
- Performance: Standalone components help reduce the overhead of modules by letting you load only the parts of the app that are needed. They help improve code splitting, reducing the overall app size.
- Simpler Routing Setup: You can use standalone components with Angular Router directly, which makes routing configuration simpler.
Key Points to Remember
- Standalone components are self-contained; they do not require NgModules for their existence.
- You must specify standalone: true in the component decorator.
- Required Angular modules (like CommonModule, FormsModule, etc.) are imported directly inside the component.
- They can be used as building blocks for applications, routed directly, and bootstrapped without relying on NgModules.
Limitations
- While standalone components simplify the structure, some complex use cases might still require NgModules for advanced features like lazy loading, or in large enterprise applications with strict organization needs.