https://angular.io/guide/pipes

Built-in Pipes

Used to transform data in the template, e.g.

<!-- Template -->
<p>Oooboy we're gonna get fancy on {{ fancyDay | date }}</p>

Some common built-in pipes are date, currency, uppercase, lowercase, decimal and percent.

Custom Pipes

Creating custom pipes is very simple, they just need to implement a transform function:

// Component
import { Pipe, PipeTransform } from `@angular/core`;

@Pipe({name: 'party'}) // 👈 pipe name to use in template
export class PartyPipe implements PipeTransform  {
	transform(value: string): string {
		return '🎉🎉🎉' + value + '🎉🎉🎉';
	}
}

Which can then be used in a template like this:

<p>Party time on {{ partyDay | date | party }}</p>