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Frequently Used Modules
An Angular app needs at least one module that serves as the root module. As you add features to your app, you can add them in modules. The following are frequently used Angular modules with examples of some of the things they contain:
| NgModule | Import it from | Why you use it |
|---|---|---|
BrowserModule |
@angular/platform-browser |
When you want to run your app in a browser |
CommonModule |
@angular/common |
When you want to use NgIf, NgFor |
FormsModule |
@angular/forms |
When you want to build template driven forms (includes NgModel) |
ReactiveFormsModule |
@angular/forms |
When you want to build reactive forms |
RouterModule |
@angular/router |
When you want to use RouterLink, .forRoot(), and .forChild() |
HttpClientModule |
@angular/common/http |
When you want to talk to a server |
Importing modules
When you use these Angular modules, import them in AppModule,
or your feature module as appropriate, and list them in the @NgModule
imports array. For example, in the basic app generated by the Angular CLI,
BrowserModule is the first import at the top of the AppModule,
app.module.ts.
/* import modules so that AppModule can access them */
import { BrowserModule } from '@angular/platform-browser';
import { NgModule } from '@angular/core';
import { AppComponent } from './app.component';
@NgModule({
declarations: [
AppComponent
],
imports: [ /* add modules here so Angular knows to use them */
BrowserModule,
],
providers: [],
bootstrap: [AppComponent]
})
export class AppModule { }
The imports at the top of the array are JavaScript import statements
while the imports array within @NgModule is Angular specific.
For more information on the difference, see JavaScript Modules vs. NgModules.
BrowserModule and CommonModule
BrowserModule imports CommonModule, which contributes many common
directives such as ngIf and ngFor. Additionally, BrowserModule
re-exports CommonModule making all of its directives available
to any module that imports BrowserModule.
For apps that run in the browser, import BrowserModule in the
root AppModule because it provides services that are essential
to launch and run a browser app. BrowserModule’s providers
are for the whole app so it should only be in the root module,
not in feature modules. Feature modules only need the common
directives in CommonModule; they don’t need to re-install app-wide providers.
If you do import BrowserModule into a lazy loaded feature module,
Angular returns an error telling you to use CommonModule instead.
More on NgModules
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