Custom Pipes in Angular 16: A Detailed Guide

Angular pipes are a powerful way to transform data in Angular applications. They can be used to format data, convert it to different units, or even perform complex calculations.

What are Angular pipes?

Angular pipes are functions that transform data. They are attached to Angular components and can be used to format data, convert it to different units, or even perform complex calculations.

For example, we can use an Angular pipe to format a date into a human-readable format, such as “January 2, 2023”. Or, we can use an Angular pipe to convert a number to a currency format, such as “$100.00”.

Different types of Angular custom pipes

There are three main types of Angular custom pipes:

• Filter pipes are used to filter data. For example, you could create a filter pipe to only show the items in an array that are greater than a certain value.
• Formatter pipes are used to format data. For example, you could create a formatter pipe to format a date into a human-readable format.
• Manipulator pipes are used to manipulate data. For example, you could create a manipulator pipe to convert a number to a currency format.

How to create Angular pipes

To create an Angular pipe, you need to create a TypeScript class that extends the PipeTransform class. The PipeTransform class has a single abstract method called transform, which takes the data to be transformed and returns the transformed data.

The following code defines an Angular pipe that formats a date into a human-readable format:

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

@Pipe({
  name: 'customDatePipe'
})
export class CustomDatePipe implements PipeTransform {

  transform(date: Date): string {
    return date.toLocaleString();
  }

}

The name property in the @Pipe decorator specifies the name of the pipe. This name will be used in the template to apply the pipe to the data.

The transform method is the most important part of the pipe class. This method takes the data to be transformed and returns the transformed data.

In this example, the transform method simply formats the date into a human-readable format.

How to use Angular pipes in your applications

To use an Angular pipe in your application, you need to import the pipe into your component and then use it in the template.

The following code imports the customDatePipe pipe into the AppComponent class:

import { Component, OnInit } from '@angular/core';
import { CustomDatePipe } from './custom-date.pipe';

@Component({
  selector: 'my-app',
  templateUrl: './app.component.html',
  styleUrls: ['./app.component.css']
})
export class AppComponent implements OnInit {

  date = new Date();

  ngOnInit() { }

}

The customDatePipe pipe is then used in the template to format the date variable:

<p>{{ date | customDatePipe }}</p>

In this example, the customDatePipe pipe is applied to the date variable in the template.
The customDatePipe pipe will then format the date variable and the result will be displayed in the p element.

Best practices for creating Angular pipes

Here are some best practices for creating Angular pipes:

• Give your pipes meaningful names.
• Make your pipes as reusable as possible.
• Avoid using side effects in your pipes.
• Test your pipes thoroughly.

Conclusion

Angular pipes are a powerful way to transform data in Angular applications. They can be used to format data, convert it to different units, or even perform complex calculations.