What sets apart the usage of :host from its absence?

Question

What sets apart the usage of :host from its absence?

I'm finding it quite confusing to understand the usage of :host in Angular.

For instance, let's consider a CSS file named a-component.component.css and its corresponding HTML file named a-component.component.html with a selector of app-a-component.

Within the CSS file, there is a rule:

h1 {
 font-size: 12px;
}

Based on the explanation provided, I believe this CSS rule only affects the <app-a-component> HTML element, is that correct?

If I modify the CSS to:

:host h1 {
 font-size: 12px;
}

(adding :host)

Will it still target the same <app-a-component> HTML element since it is the host element of this component?

If both approaches yield the same result, then why would we need to use :host if it has the same effect with or without it?

Thank you in advance!

javascript html css angular frontend

Answer 1

Answer №1

When you have :host h1 { ...} in your example, there is no distinction. The real utility of :host comes into play when you need to utilize ::ng-deep or when you want to style the host element.

For instance:

Let's say you have a component

<my-component></my-component>

and you wish to directly apply styles to that specific element. You can achieve this by using the :host selector.

:host {
  background: red;
}

This code snippet will change the background of the my-component element to red.

As for :host ::ng-deep { ..., you have the ability to deactivate ViewEncapsulation for that specific rule, but only for descendant components. If you were to simply utilize ::ng-deep without the :host, it would apply as a global style.

Answer 2

When you have :host h1 { ...} in your example, there is no distinction. The real utility of :host comes into play when you need to utilize ::ng-deep or when you want to style the host element.

For instance:

Let's say you have a component

<my-component></my-component>

and you wish to directly apply styles to that specific element. You can achieve this by using the :host selector.

:host {
  background: red;
}

This code snippet will change the background of the my-component element to red.

As for :host ::ng-deep { ..., you have the ability to deactivate ViewEncapsulation for that specific rule, but only for descendant components. If you were to simply utilize ::ng-deep without the :host, it would apply as a global style.

What sets apart the usage of :host from its absence?

Answer №1

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