Defining routes array in Angular

Introduction

We define a routes array to tell Angular which page or component to show when a user visits a specific URL. It helps users move around the app smoothly.

When you want to create a menu that links to different pages in your app.

When you want to show different components based on the URL in the browser.

When you want to protect some pages and only allow access if conditions are met.

When you want to add navigation with back and forward buttons working correctly.

When you want to organize your app into smaller parts that load only when needed.

Syntax

Angular

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

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

The routes array is an array of objects.

Each object has a path and a component or other properties like redirectTo.

Examples

This route shows HomeComponent when the URL is empty (root).

Angular

export const routes: Routes = [
  { path: '', component: HomeComponent }
];

This route uses a parameter :id to show different profiles based on the URL.

Angular

export const routes: Routes = [
  { path: 'profile/:id', component: ProfileComponent }
];

This example redirects from old-path to new-path.

Angular

export const routes: Routes = [
  { path: 'old-path', redirectTo: 'new-path', pathMatch: 'full' },
  { path: 'new-path', component: NewComponent }
];

This wildcard route catches all unknown URLs and shows a Not Found page.

Angular

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

Sample Program

This example defines four routes: 'home' and 'about' show their components, empty path redirects to 'home', and '**' catches unknown paths.

Angular

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

@Component({
  selector: 'app-home',
  template: '<h2>Home Page</h2>'
})
export class HomeComponent {}

@Component({
  selector: 'app-about',
  template: '<h2>About Page</h2>'
})
export class AboutComponent {}

@Component({
  selector: 'app-not-found',
  template: '<h2>Page Not Found</h2>'
})
export class PageNotFoundComponent {}

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

Important Notes

Routes are matched in order. The first match is used.

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

Wildcard '**' should be last to catch all unmatched routes.

Summary

Routes array tells Angular which component to show for each URL path.

Each route has a path and a component or redirectTo.

Order matters: specific routes first, wildcard last.

Practice

1. What does the routes array in Angular define?

easy

A. It defines the styles for each component.

B. It lists all services used in the app.

C. It tells Angular which component to show for each URL path.

D. It sets the database connection strings.

Solution

1. Step 1: Understand the purpose of routes array

   The routes array maps URL paths to components so Angular knows what to display.

2. Step 2: Eliminate unrelated options

   Styles, services, and database connections are not handled by routes.

3. Final Answer:

   It tells Angular which component to show for each URL path. -> Option C

4. Quick Check:

   Routes array = component mapping [OK]

Hint: Routes array links URL paths to components [OK]

Common Mistakes:

• Confusing routes with styles or services
• Thinking routes handle backend connections
• Assuming routes define component logic

2. Which of the following is the correct way to define a route for path 'home' with component HomeComponent?

easy

A. { path: 'home', component: HomeComponent }

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

C. { route: 'home', component: HomeComponent }

D. { path: 'home', component: 'HomeComponent' }

Solution

1. Step 1: Check correct property names

   The route object must have path and component properties.

2. Step 2: Verify component value type

   The component value should be the component class, not a string or redirect.

3. Final Answer:

   { path: 'home', component: HomeComponent } -> Option A

4. Quick Check:

   Use path and component keys correctly [OK]

Hint: Use component class, not string or redirectTo for components [OK]

Common Mistakes:

• Using 'route' instead of 'path'
• Setting component as a string
• Using redirectTo instead of component for components

3. Given this routes array:

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

What component will Angular show when the URL path is '/contact'?

medium

A. HomeComponent

B. AboutComponent

C. No component, error occurs

D. NotFoundComponent

Solution

1. Step 1: Match URL path to routes

   Path '/contact' does not match '' or 'about'.

2. Step 2: Use wildcard '**' route

   The '**' path catches all unmatched URLs and shows NotFoundComponent.

3. Final Answer:

   NotFoundComponent -> Option D

4. Quick Check:

   Wildcard '**' = NotFoundComponent [OK]

Hint: Unmatched paths go to '**' route component [OK]

Common Mistakes:

• Assuming empty path matches all URLs
• Thinking unmatched paths cause errors
• Confusing wildcard '**' with empty path

4. Identify the error in this routes array:

const routes = [
  { path: '', component: HomeComponent },
  { path: 'profile', redirectTo: 'user' },
  { path: 'user', component: UserComponent }
];

What is wrong with the route for 'profile'?

medium

A. redirectTo should be used with pathMatch property.

B. redirectTo cannot be used in routes array.

C. component is missing for 'profile' route.

D. Path 'user' should be capitalized.

Solution

1. Step 1: Check redirectTo usage

   When using redirectTo, Angular requires a pathMatch property to specify matching strategy.

2. Step 2: Confirm missing pathMatch causes error

   Without pathMatch, Angular cannot decide when to redirect, causing routing errors.

3. Final Answer:

   redirectTo should be used with pathMatch property. -> Option A

4. Quick Check:

   redirectTo needs pathMatch [OK]

Hint: Always add pathMatch with redirectTo routes [OK]

Common Mistakes:

• Omitting pathMatch with redirectTo
• Thinking redirectTo needs component
• Assuming path names must be capitalized

5. You want to define routes so that:
- The home page shows HomeComponent at path ''.
- The about page shows AboutComponent at path 'about'.
- Any unknown path redirects to home.

Which routes array correctly implements this?

hard

A. [
{ path: '', component: HomeComponent },
{ path: 'about', component: AboutComponent },
{ path: '**', redirectTo: '' }
]

B. [
{ path: '', component: HomeComponent },
{ path: 'about', component: AboutComponent },
{ path: '**', redirectTo: '', pathMatch: 'full' }
]

C. [
{ path: '', component: HomeComponent },
{ path: 'about', component: AboutComponent },
{ path: '*', redirectTo: '', pathMatch: 'full' }
]

D. [
{ path: '', component: HomeComponent },
{ path: 'about', component: AboutComponent },
{ path: '**', component: HomeComponent }
]

Solution

1. Step 1: Check wildcard path for unknown URLs

   The wildcard path for unknown URLs is '**', not '*'.

2. Step 2: Confirm redirectTo usage with pathMatch

   Redirect routes must include pathMatch: 'full' to work properly.

3. Step 3: Verify redirect target and components

   Redirecting '**' to '' sends unknown URLs to home page correctly.

4. Final Answer:

   [ { path: '', component: HomeComponent }, { path: 'about', component: AboutComponent }, { path: '**', redirectTo: '', pathMatch: 'full' } ] -> Option B

5. Quick Check:

   Use '**' with redirectTo and pathMatch 'full' [OK]

Hint: Use '**' wildcard with redirectTo and pathMatch 'full' [OK]

Common Mistakes:

• Using '*' instead of '**' for wildcard
• Omitting pathMatch in redirectTo routes
• Using component instead of redirectTo for redirects