RouterModule configuration in Angular

Introduction

RouterModule helps your Angular app switch between different pages or views without reloading the whole page.

You want to create a multi-page app with different URLs.

You need to show different components based on the URL path.

You want to add navigation links that change the view smoothly.

You want to protect some pages and redirect users if needed.

Syntax

Angular

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

const routes: Routes = [
  { path: 'home', component: HomeComponent },
  { path: 'about', component: AboutComponent },
  { path: '', redirectTo: 'home', pathMatch: 'full' },
  { path: '**', component: NotFoundComponent }
];

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

The routes array defines URL paths and which component to show.

RouterModule.forRoot(routes) sets up the router with your routes.

Examples

Simple route for a dashboard page.

Angular

const routes: Routes = [
  { path: 'dashboard', component: DashboardComponent }
];

Redirect empty path to dashboard.

Angular

const routes: Routes = [
  { path: '', redirectTo: 'dashboard', pathMatch: 'full' }
];

Catch-all route for unknown URLs.

Angular

const routes: Routes = [
  { path: '**', component: PageNotFoundComponent }
];

Sample Program

This example sets up a simple Angular app with three routes: home, about, and a fallback for unknown pages. Navigation links let you switch pages without reloading. The router-outlet shows the matched component.

Angular

import { Component } from '@angular/core';
import { RouterModule, Routes } from '@angular/router';
import { bootstrapApplication } from '@angular/platform-browser';

@Component({
  selector: 'app-home',
  standalone: true,
  template: `<h2>Home Page</h2><p>Welcome to the home page!</p>`
})
class HomeComponent {}

@Component({
  selector: 'app-about',
  standalone: true,
  template: `<h2>About Page</h2><p>Learn more about us here.</p>`
})
class AboutComponent {}

@Component({
  selector: 'app-not-found',
  standalone: true,
  template: `<h2>Page Not Found</h2><p>Sorry, this page does not exist.</p>`
})
class NotFoundComponent {}

const routes: Routes = [
  { path: 'home', component: HomeComponent },
  { path: 'about', component: AboutComponent },
  { path: '', redirectTo: 'home', pathMatch: 'full' },
  { path: '**', component: NotFoundComponent }
];

@Component({
  selector: 'app-root',
  standalone: true,
  imports: [RouterModule, HomeComponent, AboutComponent, NotFoundComponent],
  template: `
    <nav>
      <a routerLink="/home" aria-label="Go to Home page">Home</a> |
      <a routerLink="/about" aria-label="Go to About page">About</a>
    </nav>
    <main>
      <router-outlet></router-outlet>
    </main>
  `
})
class AppComponent {}

bootstrapApplication(AppComponent, {
  providers: [
    RouterModule.forRoot(routes)
  ]
});

Important Notes

Always include a wildcard ** route to catch unknown URLs and show a friendly message.

Use pathMatch: 'full' when redirecting empty paths to avoid partial matches.

Remember to add RouterModule to your component imports and exports for routing to work.

Summary

RouterModule lets Angular apps switch views based on URL paths.

Define routes as an array of path-component pairs.

Use RouterModule.forRoot(routes) to set up routing in your app.

Practice

1. What is the main purpose of RouterModule.forRoot(routes) in an Angular app?

easy

A. To create a new Angular component

B. To configure the app's routes and enable navigation based on URL paths

C. To style the app's components

D. To fetch data from a server

Solution

1. Step 1: Understand RouterModule role

   RouterModule is used to manage navigation and views based on URL paths in Angular.

2. Step 2: Role of forRoot method

   The forRoot method sets up the routes for the whole app, telling Angular which component to show for each path.

3. Final Answer:

   To configure the app's routes and enable navigation based on URL paths -> Option B

4. Quick Check:

   RouterModule.forRoot sets routes [OK]

Hint: Remember: forRoot sets main routes once per app [OK]

Common Mistakes:

• Confusing forRoot with creating components
• Thinking RouterModule styles components
• Assuming it fetches data

2. Which of the following is the correct syntax to import RouterModule with routes in an Angular module?

easy

A. RouterModule(routes)

B. imports: RouterModule.forRoot(routes)

C. imports: [RouterModule.forRoot(routes)]

D. RouterModule.import(routes)

Solution

1. Step 1: Check Angular module imports syntax

   Angular modules expect an array for the imports property.

2. Step 2: Correct use of RouterModule.forRoot

   RouterModule.forRoot(routes) returns a module configured with routes and must be inside an array.

3. Final Answer:

   imports: [RouterModule.forRoot(routes)] -> Option C

4. Quick Check:

   Imports must be an array with forRoot call [OK]

Hint: Always wrap RouterModule.forRoot in an array for imports [OK]

Common Mistakes:

• Omitting the array brackets in imports
• Using RouterModule.import which doesn't exist
• Calling RouterModule as a function directly

3. Given this route configuration:

const routes = [
  { path: '', component: HomeComponent },
  { path: 'about', component: AboutComponent }
];

What component will Angular display when the URL path is /about?

medium

A. AboutComponent

B. HomeComponent

C. No component, shows error

D. Both HomeComponent and AboutComponent

Solution

1. Step 1: Match URL path to route

   The URL path '/about' matches the route with path 'about'.

2. Step 2: Identify component for matched route

   The route with path 'about' uses AboutComponent.

3. Final Answer:

   AboutComponent -> Option A

4. Quick Check:

   Path '/about' shows AboutComponent [OK]

Hint: Match URL path exactly to route path to find component [OK]

Common Mistakes:

• Assuming empty path '' matches '/about'
• Thinking multiple components show at once
• Expecting error for valid path

4. Identify the error in this RouterModule configuration:

const routes = [
  { path: 'home', component: HomeComponent },
  { path: 'profile' component: ProfileComponent }
];

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

medium

A. Routes array should be inside imports array

B. RouterModule.forRoot should be RouterModule.forChild

C. AppRoutingModule should not export RouterModule

D. Missing comma between 'profile' path and component property

Solution

1. Step 1: Check routes array syntax

   Between 'path: 'profile'' and 'component: ProfileComponent' a comma is missing, causing syntax error.

2. Step 2: Verify RouterModule usage and exports

   Using RouterModule.forRoot(routes) and exporting RouterModule is correct here.

3. Final Answer:

   Missing comma between 'profile' path and component property -> Option D

4. Quick Check:

   Comma missing in object properties causes error [OK]

Hint: Check commas between object properties in routes [OK]

Common Mistakes:

• Confusing forRoot and forChild usage
• Placing routes array incorrectly
• Removing exports of RouterModule

5. You want to add a default route that redirects empty path '' to '/home' using RouterModule. Which configuration is correct?

hard

A. { path: '', redirectTo: '/home', pathMatch: 'full' }

B. { path: '', redirectTo: 'home' }

C. { path: '', component: HomeComponent, redirectTo: '/home' }

D. { redirectTo: '/home', path: '', pathMatch: 'prefix' }

Solution

1. Step 1: Understand redirectTo usage

   To redirect from '' path, use redirectTo with full path and specify pathMatch as 'full' to match exact empty path.

2. Step 2: Check options for correct syntax

   { path: '', redirectTo: '/home', pathMatch: 'full' } correctly uses redirectTo with '/home' and pathMatch: 'full'. { path: '', redirectTo: 'home' } misses pathMatch, C wrongly combines component and redirectTo, D uses 'prefix' which causes partial matching issues.

3. Final Answer:

   { path: '', redirectTo: '/home', pathMatch: 'full' } -> Option A

4. Quick Check:

   Redirect empty path with pathMatch 'full' [OK]

Hint: Use pathMatch: 'full' when redirecting empty path [OK]

Common Mistakes:

• Omitting pathMatch property
• Combining component with redirectTo
• Using pathMatch: 'prefix' for empty path redirect