How to navigate between components

• Almost any web application needs navigation
• SPA's navigation = routing to a component and show it on the web page
• For our news app we will create a MenuComponent for our navigation links
  • The menu will contain 2 links:
    • home = home page
    • article = article page

Home component

• Create the HomeComponent by executing the following command in the src/app folder:

ng g c home-component

• Remove the dummy paragraph and add the following HTML to the home-component.html file:

<h1>Welcome home</h1>
<p>This is the homepage of our news app!</p>

Menu component

• Create the MenuComponent by executing the following command in the src/app folder:

ng g c menu-component

• Remove the dummy paragraph and add the following HTML to the menu-component.html file:

<nav>
  <ul>
    <li><a href="#">Home</a></li>
    <li><a href="#">Article</a></li>
  </ul>
</nav>

Routing

• To define how users navigate through your application, you use routes
• Angular has an easy to use built-in routing system

app.routes.ts

• When we created our application we already get a app.routes.ts file
• This file is by default used to specify the routes in our application
• Let's add two routes to the routes array:

import { Routes } from '@angular/router';
import { ArticleComponent } from './article-component/article-component';
import { HomeComponent } from './home-component/home-component';

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

Routes

• We've created 2 routes - path: '' = root/default route which starts/initializes/opens the HomeComponent - path: 'article' opens the ArticleComponent when visiting http://localhost:5878/article

• The routes configured in the app.routes are provided to your application through the app.config.ts:

import { ApplicationConfig, provideBrowserGlobalErrorListeners, provideZonelessChangeDetection } from '@angular/core';
import { provideRouter } from '@angular/router';

import { routes } from './app.routes';

export const appConfig: ApplicationConfig = {
  providers: [
    provideBrowserGlobalErrorListeners(),
    provideZonelessChangeDetection(),
    provideRouter(routes)
  ]
};

<router-outlet></router-outlet>

• Somewhere in a component you need to preserve some space for the components you navigate to
• The perfect place for this is the app.html, so modify the HTML:

<app-menu-component></app-menu-component>

<router-outlet></router-outlet>

• The MenuComponent must be added to the imports array in the AppComponent, because we use it directly in our app.html
• The HomeComponent and ArticleComponent don't have to be imported, because we will navigate to them through routing!

//app.ts
import { Component, signal } from '@angular/core';
import { RouterOutlet } from '@angular/router';
import { MenuComponent } from "./menu-component/menu-component";

@Component({
  selector: 'app-root',
  imports: [RouterOutlet, MenuComponent],
  templateUrl: './app.html',
  styleUrl: './app.css'
})
export class App {
  protected readonly title = signal('my-news');
}

MenuComponent & router-outlet

• app-menu-component = MenuComponent: this shows our navigation menu
• router-outlet = placeholder for components you navigate to via routing
  • calling the article route will load the ArticleComponent in the router-outlet directive
• When we start our app (http://localhost:5878/) the HomeComponent is loaded (path: '')

• Let's finish our navigation links in the menu-component.html:

<nav>
    <ul>
        <li><a routerLink="/" routerLinkActive="active" [routerLinkActiveOptions]="{ exact: true }">Home</a></li>
        <li><a routerLink="/article" routerLinkActive="active" [routerLinkActiveOptions]="{ exact: true }">Article</a></li>
    </ul>
</nav>

code	description
routerLink="/"	path we defined in the routes-array in the AppRoutingModule
routerLinkActive="active"	Toggles CSS classes for the active link (in this case the active class).
[routerLinkActiveOptions]="{ exact: true }"	By default, the default route will always be the active route, because Angular only checks if the URL contains the route path. In case of the default route ('/') this always is true. To fix this we add the [routerLinkActiveOptions]="{ exact: true }" directive to every a tag

Can't bind to 'routerLinkActiveOptions'

• This error means that our MenuComponent has to little information to set up the routing
• We have to import the RouterModule to be able to make use of all the Routing functionalities!
• menu.component.ts:

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

@Component({
  selector: 'app-menu-component',
  imports: [RouterModule],
  templateUrl: './menu-component.html',
  styleUrl: './menu-component.css'
})
export class MenuComponent {

}

• Finally add some CSS in menu.component.css to prettify our menu:

nav ul {
    display: flex;
    list-style-type: none;
    padding: 0px;
}

nav li {
    flex: 1 1 auto;
    display: flex;
}

nav a {
    flex: 1 1 auto;
    text-decoration: none;
    text-align: center;
    padding: 20px;
    background-color: lightgrey;
    color: black;
}

nav a.active {
    background-color: lightsalmon;
    color: black;
}

nav a:hover {
    color: lightgrey;
    background-color: grey;
}

• When the link is active, Angular will add the active class to this link (because we specified it)
• Therefore we apply some styling for an active link

Result:

No page refresh

• Notice how the page is not fully reloaded/refreshed!
• There is no interaction with a server to get a page/component
• Angular has a built-in Change Detection system which updates the current view with the new component

Exercise

Take a backup of the current state of your application (or create a new branch)

• Add a third "tab" named "contact" at the top of your application
• Set the correct routes and create the correct component "contact"
• Add some static content with basic details about yourself