In this tutorial, we will learn how to lazy load modules in Angular 13 using dynamic imports.

What is Lazy Loading?

Lazy loading is the way to download only when it requires or in chunks instead of bigger pieces.

In this tutorial, we will use dynamic imports and loadChildren properties to achive lazy loading in Angular.

Create Angular Application

Run the following command to install the latest version of Angular CLI:

npm install -g @angular/cli

Install a new angular application:

ng new angular-lazy-load-sample

Navigate to the project root:

cd angular-lazy-load-sample

Generate Angular Module

Lazy loading is entirely dependent on modules,so  execute the below command from the command prompt to generate module:

ng generate module user

Add two-component inside user module using below command:

ng generate component user/list
ng generate component user/user-details

Lazy Load with LoadChildren

With using loadChildren property, we can lazy load modules as follows:

import { NgModule } from '@angular/core';
import { Routes, RouterModule } from '@angular/router';

const routes: Routes = [
  { 
    path: 'user', 
    loadChildren: () => import(`./user/user.module`).then(
      module => module.UserModule
    )
  },
];

@NgModule({
  imports: [RouterModule.forRoot(routes)],
  exports: [RouterModule]
})

export class AppRoutingModule { }

Setting Up Routes

Here, we need to create a separate user routing, which will handle the lazy-loading for the components associated with it.

ng g m user/user --routing

Now, import the components  to blog module and pass them in routes array.

Then go to user/user-routing.module.ts file and add the following code:

import { NgModule } from '@angular/core';
import { Routes, RouterModule } from '@angular/router';

import { ListComponent } from '../list/list.component';
import { UserDetailsComponent } from '../user-details/user-details.component';

const routes: Routes = [
  { path: '', component: ListComponent },
  { path: 'user-details', component: UserDetailsComponent }  
];

@NgModule({
  imports: [RouterModule.forChild(routes)],
  exports: [RouterModule]
})

export class UserRoutingModule { }

Above we have defined the routes for list and User Details components within the UserRoutingModule.

Next, go to user.module.ts and place the following code:

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

import { UserRoutingModule } from './user/user-routing.module';

import { ListComponent } from './list/list.component';
import { UserDetailsComponent } from './user-details/user-details.component';

@NgModule({
  imports: [
    CommonModule,
    UserRoutingModule
  ],
  declarations: [ListComponent, UserDetailsComponent]
})

export class UserModule { }

Now its done, our application lazy-loaded successfully, you can check it by navigating to network tab in developer tools.

Conclusion:

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