excerpt.pipe.ts

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

@Pipe({ name: 'excerpt' })
export class ExcerptPipe implements PipeTransform {
  transform(text: string, limit: number = 5) {
    if (text.length <= limit) {
      return text;
    }
    return text.substring(0, limit) + '...';
  }
}

get-value-by-key.pipe.ts

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

@Pipe({
  name: 'getValueByKey',
  pure: false
})
export class GetValueByKeyPipe implements PipeTransform {
  transform(value: any[], id: number, property: string): any {
    const filteredObj = value.find(item => {
      if (item.id !== undefined) {
        return item.id === id;
      }

      return false;
    });

    if (filteredObj) {
      return filteredObj[property];
    }
  }
}

relative-time.pipe.ts

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

@Pipe({ name: 'relativeTime' })
export class RelativeTimePipe implements PipeTransform {
  transform(value: Date) {
    if (!(value instanceof Date)) {
      value = new Date(value);
    }

    const seconds: number = Math.floor(((new Date()).getTime() - value.getTime()) / 1000);
    let interval: number = Math.floor(seconds / 31536000);

    if (interval > 1) {
      return interval + ' years ago';
    }
    interval = Math.floor(seconds / 2592000);
    if (interval > 1) {
      return interval + ' months ago';
    }
    interval = Math.floor(seconds / 86400);
    if (interval > 1) {
      return interval + ' days ago';
    }
    interval = Math.floor(seconds / 3600);
    if (interval > 1) {
      return interval + ' hours ago';
    }
    interval = Math.floor(seconds / 60);
    if (interval > 1) {
      return interval + ' minutes ago';
    }
    return Math.floor(seconds) + ' seconds ago';
  }
}

shared-pipes.module.ts

import { NgModule } from '@angular/core';
import { CommonModule } from '@angular/common';
import { ExcerptPipe } from './excerpt.pipe';
import { GetValueByKeyPipe } from './get-value-by-key.pipe';
import { RelativeTimePipe } from './relative-time.pipe';

const pipes = [
  ExcerptPipe,
  GetValueByKeyPipe,
  RelativeTimePipe
];

@NgModule({
  imports: [
    CommonModule
  ],
  declarations: pipes,
  exports: pipes
})
export class SharedPipesModule { }