How to apply css class to a component element when it's created by router-outlet?

Question

I have DOM that looks something like this:

    
    ...



        

Answer 1

Assuming you always want the class applied to this component, you can use host in your component metadata:

@Component({
  selector:'project',
  host: {
      class:'classYouWantApplied'
  }
})

Resulting in:

<app>
    <router-outlet></router-outlet>
    <project class="classYouWantApplied">...</project>
</app>

Answer 2

Currently, Angular 6 recommends me to use @HostBindings and @HostListeners instead of the host property:

export class ProjectComponent {
  @HostBinding('class') classes = 'classYouWantApplied';
}

Answer 3

You can do this with a HostBinding, which is effectively the same as using the host property that has already been mentioned, although that method throws a TSLint error with default listing rules.

In your component on which you want to apply a class:

import { Component, HostBinding, Host (optional for typing) } from '@angular/core';

@Component({...})
export class GiveMeAClassComponent {
    @HostBinding('class.some-class') someClass: Host = true;
    ...
}

And then in your root styles.scss file, you can add the following:

.some-class {
    // Styles in here will now be applied to your GiveMeAClassComponent at a root level
}

Answer 4

I created a RouterOutletHelperDirective which can be modified as necessary.

Your use-case may be different but for me :

• I needed to set a default set of classes on each router-outlet generated item
• I needed to prevent this default based on certain conditions, such as ActivatedRoute data.

You use it like this (the class is optional):

<router-outlet routerOutletHelper
               [routerOutletHelperClass]="'blue-border'"></router-outlet>

Then create the directive, add and export it to your app module.

import { Directive, ElementRef, Renderer2, Input } from "@angular/core";
import { RouterOutlet } from "@angular/router";
import { Subscription } from "rxjs";

@Directive({
    selector: 'router-outlet[routerOutletHelper]'
})
export class RouterOutletHelperDirective
{
    constructor(private routerOutlet: RouterOutlet,
                private element: ElementRef<HTMLElement>,
                private renderer: Renderer2) { }

    subscription = new Subscription();

    @Input('routerOutletHelperClass')
    customClassName: string | undefined;

    ngOnInit() 
    {
        this.subscription.add(this.routerOutlet.activateEvents.subscribe((_evt: any) => {

            // find the component element that was just added
            const componentElement = this.element.nativeElement.nextSibling;

            // add a custom class
            if (this.customClassName) 
            {
                this.renderer.addClass(componentElement, this.customClassName);
            }

            // add my default classes, unless the activated route data 
            // (specified in module routing file) has { addDefaultClasses: false }
            if (this.routerOutlet.activatedRouteData && this.routerOutlet.activatedRouteData.addDefaultClasses !== false)
            {
                // these are my application's default classes (material / theming)
                // (an additional data parameter could be 'darkTheme: boolean')
                this.renderer.addClass(componentElement, 'mat-typography');
                this.renderer.addClass(componentElement, 'rr-theme-light');
            }
        }));
    }

    ngOnDestroy()
    {    
        this.subscription.unsubscribe();
    }
}

Answer 5

For me it helped to wrap the router-outlet into another container.

<div class="classYouWantApplied">
  <router-outlet>
</div>

Like this you could apply the class to the surrounding container.