Make it Accessible: Navigation in Angular
Today, we are gonna talk about navigation. Let's start from the beginning. What's navigation?
Web navigation refers to the process of navigating a network of information resources in the World Wide Web
Wikipedia
In those terms, we could say that when a user clicks a link, a navigation event is triggered, the browser captures this event, and then redirects the user to a new page. In pure HTML, this forces the browser to load the entire html. When you use Angular, things are different. The browser doesn't need to load the whole html again. Instead, by using AJAX, you get only what was changed.
I thought that was a magical thing, and that the benefits were huge in comparison to the way HTML links normally behave. But that's true only until a certain point when you want to make accessible applications, things get more complicated. Why? If you have read my last article, Make it Accessible, you know how important HTML5 semantic elements are.
If you haven't read it. You can access here: Make it Accessible: Headings in Angular
Just like native HTML buttons can help make things more accessible out of the box by providing keyboard support and focus ability, anchors are here to make your life easier.
Anchors to the rescue
In pure HTML, we use anchor elements with the href attribute. That way, we can tell the browser to which url it has to redirect the user upon click. This triggers a full load of the app, BUT there's a benefit to it: its support of web accessibility. Screen reader users are used to the way native HTML navigation works. It helps by reading the title of the new page, and setting the focus to the top of the document, also by having the title of the page change, so the user knows the current location.
So it basically allows:
- Sighted users to know the current page by reading the title
- Visually impaired users to know the current page from a screen reader announcing the title
- Setting focus to the top of the document
If you have used the Angular Router, you know that all the accessibility features just mentioned are lost. So, if you are looking to make your Angular app more accessible, sooner than later, you are gonna have to face this.
We are gonna solve each of the problems, one at a time. If you want to do all the coding processes on your own, access this broken version of the code, and follow my lead.
Current page for Sighted Users
In this step, we are going to focus on making sure the user has a way to know what the current page is. In the code I just gave you, you'll find a simple app with a header and some navigation. Right now, there's no way for the user to know the current page (besides reading the url, hoping it's as readable as in the example).
This could be solved by having a different color for the currently active link in the header, so let's do that.
First, we'll need to use the routerLinkActive directive in the anchors from the navigation. For this, we need to go to the src/app/app.component.html file and replace the nav element with this one.
<nav class="header__nav">
<ul>
<li>
<a routerLink="/page-a" routerLinkActive="active">Page A</a>
</li>
<li>
<a routerLink="/page-b" routerLinkActive="active">Page B</a>
</li>
</ul>
</nav>
So now, Angular will make sure to add the class active to the anchor which route is currently active. Let's change the color of the active anchor. Go to the file src/app/app.component.scss, and add a color white when it has the active class.
a {
// ...
&.active {
color: white;
}
}
Make sure to put the
&.activeselector after all the ones that are already there.
Is the navigation accessible? Well, not really. What about color blind users? We need to give them a way to know. For that, we'll add underline and outline to the active anchor. Let's go back to the src/app/app.component.scss file.
a {
// ...
&.active,
&:hover,
&:focus {
color: white;
outline: 1px solid white;
}
&.active {
text-decoration: underline;
}
}
Since the hover and focus have the outline and the color that we want, I reorganized the selectors to reduce the duplicated code.
Last thing we have to do is to make sure we update the title of the page for every time the url changes. For this, I followed the instructions from Todd Motto in his article Dynamic page titles in Angular 2 with router events and did some changes to it.
This leads us to changing the src/app/app-routing.module.ts
const routes: Routes = [
{
path: 'page-a',
data: { title: 'I am the super Page A' },
loadChildren: () =>
import('./page-a/page-a.module').then(m => m.PageAModule)
},
{
path: 'page-b',
data: { title: 'I am the not that super Page B' },
loadChildren: () =>
import('./page-b/page-b.module').then(m => m.PageBModule)
}
];
The key here is that I included a data property to each route and gave each a title. Next, we have to update the src/app/app.component.ts file.
//...
import {
map,
distinctUntilChanged,
startWith,
filter,
mergeMap
} from 'rxjs/operators';
import { Router, ActivatedRoute, NavigationEnd } from '@angular/router';
import { Title } from '@angular/platform-browser';
@Component({
selector: 'app-root',
templateUrl: './app.component.html',
styleUrls: ['./app.component.scss']
})
export class AppComponent {
// ...
title$: Observable<string>;
constructor(
private router: Router,
private activatedRoute: ActivatedRoute,
private titleService: Title
) {}
ngOnInit() {
// Get the activated route on Navigation end
const route$ = this.router.events.pipe(
filter(event => event instanceof NavigationEnd),
map(() => this.activatedRoute)
);
// Get the first child route AKA the root
const primaryRoute$ = route$.pipe(
map(route => {
while (route.firstChild) route = route.firstChild;
return route;
}),
filter(route => route.outlet === 'primary')
);
// Get the first child route AKA the root
const routeData$ = primaryRoute$.pipe(mergeMap(route => route.data));
// Get the actual title from the route data
this.title$ = routeData$.pipe(map(({ title }) => title));
this.title$.subscribe(title => {
// Set title to the page
this.titleService.setTitle(title);
});
}
}
Above, I injected the services we need, made a stream from the router events in order to get the current title, and changed it in the browser using the Title service. If you want to learn more of this, you can read Todd Motto's article.
You have just solved the first problem.
Current page for Unsighted Users
You are here for accessibility, so it's time for visually impaired users to be taken into account. For this you can use the aria-live attribute.
Simple content changes, which are not interactive, should be marked as live regions.
MDN Web Docs
That seems to be our use case- we want to announce to users when there was a page transition. For that we'll create an element with aria-live, containing the title content.
To get started, go to the src/app/app.component.html file, and use Angular's async pipe to render the title.
<div *ngIf="title$ | async as title" aria-live="assertive">
<span [attr.aria-label]="title"></span>
</div>
If we put the title inside the span, instead of using aria-label, we would need to hide this element from sighted users, this is a little trick I love to do instead. Also, notice that we use the aria-live property with assertive to make sure this gets announced as soon as possible.
NOTE: Normally, I wouldn't use the ngIf in the tag with the aria-live because it will start announcing after it gets instantiated. In this case that's exactly what we need because we dont want to announce the title again on first load.
Now every user using the app will know on which page they are, no matter their condition. We are almost there to make a more inclusive navigation.
Manage focus and scroll
Lets make things even better now. You have probably noticed that whenever an Angular page transition occurs, if its possible, the scroll is retained in the same position, unless the page we have just transitioned to has a height that is less than the current scroll. So the first step would be to set the scroll to the very top on every page transition.
Just go back to the src/app/app.component.ts file and do this:
// ...
@Component({
selector: 'app-root',
templateUrl: './app.component.html',
styleUrls: ['./app.component.scss']
})
export class AppComponent {
// ...
ngOnInit() {
// ...
this.title$.subscribe(title => {
// ...
// Scroll to top
window.scrollTo(0, 0);
// ...
});
}
// ...
}
Add a call to the scrollTo method from window using the parameters (0, 0), that way we tell the browser to scroll to the top of the document.
Whenever a page transition occurs in a pure HTML website, the focus is cleared and set to the first focusable element in the document. It is slightly harder but there's a trick for that, so let's do it together. Go again to the same file, and do this:
import { /* ... */ ViewChild, ElementRef } from '@angular/core';
// ...
@Component({
selector: 'app-root',
templateUrl: './app.component.html',
styleUrls: ['./app.component.scss']
})
export class AppComponent {
// ...
@ViewChild('appHeader', { static: true }) appHeader: ElementRef;
ngOnInit() {
// ...
this.title$.subscribe(title => {
// ...
// Set focus to the appHeader
this.appHeader.nativeElement.focus();
// ...
});
}
// ...
}
This is almost as easy as the step before, but instead of just calling a method on the window object, we have to create a reference to an element in the DOM. We've used ViewChild decorator for that. So now, we are setting the title, moving the scroll to top and setting the focus to the header in the title$ subscription.
Don't forget to add the template reference in src/app/app.component.ts and making it focusable.
<header class="header" tabindex="-1" #appHeader>
<!-- ... -->
</header>
We dont want the focus outline in the header, so you can do this:
.header {
// ...
&:focus {
outline: none;
}
// ...
}
Conclusion
After playing a little bit with Angular, we were able to make the navigation feel like the native one. It's not the most accessible navigation in the world, but this can get you there and is WAY BETTER than nothing. If you want a finished solution, look at this working version of the app.
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