Custom pipe for showing summary text in angular

excerpt.pipe.ts

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

@Pipe({
  name: "excerpt"
})

export class ExcerptPipe implements PipeTransform{
  
  transform(text: string, limit?: number){

    if(!text) return null;

    let desiredLimit = (limit) ? limit : 50;

    return text.substr(0, desiredLimit) + '...';
  
  }

}

// exapmle: {{ text | excerpt : 10 }}