In Angular, how do you determine the active route?

Question

NOTE: There are many different answers here, and most have been valid at one time or another. The fact is that what works has changed a number of times as the Angular team has changed its Router. The Router 3.0 version that will eventually be the router in Angular breaks many of these solutions, but offers a very simple solution of its own. As of RC.3, the preferred solution is to use [routerLinkActive] as shown in this answer.

In an Angular application (current in the 2.0.0-beta.0 release as I write this), how do you determine what the currently active route is?

I'm working on an app that uses Bootstrap 4 and I need a way to mark navigation links/buttons as active when their associated component is being shown in a <router-output> tag.

I realize that I could maintain the state myself when one of the buttons is clicked upon, but that wouldn't cover the case of having multiple paths into the same route (say a main navigation menu as well as a local menu in the main component).

Any suggestions or links would be appreciated. Thanks.

Answer 1

With the new Angular router, you can add a [routerLinkActive]="['your-class-name']" attribute to all your links:

<a [routerLink]="['/home']" [routerLinkActive]="['is-active']">Home</a> 

Or the simplified non-array format if only one class is needed:

<a [routerLink]="['/home']" [routerLinkActive]="'is-active'">Home</a> 

Or an even simpler format if only one class is needed:

<a [routerLink]="['/home']" routerLinkActive="is-active">Home</a> 

See the poorly documented routerLinkActive directive for more info. (I mostly figured this out via trial-and-error.)

UPDATE: Better documentation for the routerLinkActive directive can now be found here. (Thanks to @Victor Hugo Arango A. in the comments below.)