In Angular, how do you determine the active route?

Small improvement to @alex-correia-santos answer based on https://github.com/angular/angular/pull/6407#issuecomment-190179875

import {Router, RouteConfig, ROUTER_DIRECTIVES} from 'angular2/router';
// ...
export class App {
  constructor(private router: Router) {
  }

  // ...

  isActive(instruction: any[]): boolean {
    return this.router.isRouteActive(this.router.generate(instruction));
  }
} 

And use it like this:

<ul class="nav navbar-nav">
    <li [class.active]="isActive(['Home'])">
        <a [routerLink]="['Home']">Home</a>
    </li>
    <li [class.active]="isActive(['About'])">
        <a [routerLink]="['About']">About</a>
    </li>
</ul>

I've replied this in another question but I believe it might be relevant to this one as well. Here's a link to the original answer: Angular 2: How to determine active route with parameters?

I've been trying to set the active class without having to know exactly what's the current location (using the route name). The is the best solution I have got to so far is using the function isRouteActive available in the Router class.

router.isRouteActive(instruction): Boolean takes one parameter which is a route Instruction object and returns true or false whether that instruction holds true or not for the current route. You can generate a route Instruction by using Router's generate(linkParams: Array). LinkParams follows the exact same format as a value passed into a routerLink directive (e.g. router.isRouteActive(router.generate(['/User', { user: user.id }])) ).

This is how the RouteConfig could look like (I've tweaked it a bit to show the usage of params):

@RouteConfig([
  { path: '/', component: HomePage, name: 'Home' },
  { path: '/signin', component: SignInPage, name: 'SignIn' },
  { path: '/profile/:username/feed', component: FeedPage, name: 'ProfileFeed' },
])

And the View would look like this:

<li [class.active]="router.isRouteActive(router.generate(['/Home']))">
   <a [routerLink]="['/Home']">Home</a>
</li>
<li [class.active]="router.isRouteActive(router.generate(['/SignIn']))">
   <a [routerLink]="['/SignIn']">Sign In</a>
</li>
<li [class.active]="router.isRouteActive(router.generate(['/ProfileFeed', { username: user.username }]))">
    <a [routerLink]="['/ProfileFeed', { username: user.username }]">Feed</a>
</li>

This has been my preferred solution for the problem so far, it might be helpful for you as well.

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.)