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Getting Started with Pipes in Angular: A Beginner's Guide

Getting Started with Pipes in Angular: A Beginner's Guide

Ayush Agarwal's photo
Ayush Agarwal
·Apr 19, 2023·

9 min read

Table of contents

Angular is a powerful front-end framework for building dynamic and scalable web applications. One of the many features that make Angular so popular is its ability to manipulate and transform data in real-time using pipes. Pipes allow developers to transform data values in templates and component classes without modifying the original data source.

Pipes are an essential tool for creating reusable and modular code in Angular.

If you are new to Angular or looking to expand your knowledge of the framework, this blog is a great place to start. We will cover the fundamentals of pipes, explore their benefits, and delve into both built-in and custom pipes in Angular.

By the end of this blog, you will have a comprehensive understanding of pipes in Angular, and you'll be equipped with the knowledge you need to create efficient and maintainable code in your Angular projects.

Prerequisites

To get the most out of this blog, you should have a basic understanding of Angular fundamentals, such as components, modules, and templates. It is recommended that you have some experience with TypeScript and JavaScript, as well as a working installation of the Angular CLI.

Let's dive into the world of pipes and take your Angular skills to the next level!

Introduction to Pipes in Angular

Pipes are a powerful feature of the Angular framework that allows developers to transform data values easily in templates and component classes without modifying the original data source. Pipes are an essential tool for creating reusable and modular code in Angular.

What are pipes?

In Angular, pipes are used to transform data from one format to another. They can be used to modify strings, numbers, dates, and arrays, and can also be chained together to create complex transformations.

Pipes are defined and used in templates by enclosing the target value in a pipe character ( | ) followed by the pipe name and any parameters.

Angular comes with several built-in pipes that are commonly used, such as the DatePipe, UpperCasePipe, and LowerCasePipe. Custom pipes can also be created to suit the specific requirements of an application.

Why are pipes useful in Angular?

Pipes provide a powerful and flexible way to transform data in real-time, without modifying the original data source. They make it easy to format data for display, filter large data sets, and perform calculations on data values.

Overall, pipes are an essential feature of the Angular framework that enables developers to create flexible, maintainable, and scalable applications. In the next section, we will explore the different types of built-in pipes that are available in Angular.

Built-in Pipes in Angular

Angular provides several built-in pipes that can be used to transform data in a variety of ways. These pipes can be used in templates and component classes to format, filter, and manipulate data values.

Commonly used pipes in Angular:

Some of the most commonly used built-in pipes in Angular include:

  1. DatePipe: This pipe is used to format date values into a specific format. The pipe accepts a date string or a Date object and returns a formatted date string.

  2. CurrencyPipe: This pipe is used to format currency values with the appropriate currency symbol and formatting based on the current locale. The pipe accepts a number and an optional currency code and returns a formatted currency string.

  3. PercentPipe: This pipe is used to format numeric values as a percentage with a specified number of decimal places. The pipe accepts a number and an optional number of decimal places and returns a formatted percentage string.

Syntax and examples of each pipe:

The syntax for using pipes in Angular templates is as follows:

{{ value | pipeName: parameter1: parameter2... }}

Here, value is the data value to be transformed, pipe name is the name of the pipe, and parameters are optional parameters that can be used to customize the transformation.

For example, to format a date value using the DatePipe, the following syntax can be used:

<!-- currentDate is a Date object with the value of today's date -->
<p> Today's date is {{ currentDate | date:'fullDate' }} </p>

<!-- Output --> 
<!-- Today's date is Monday, April 19, 2023 -->

In this example, the currentDate variable is transformed using the DatePipe and the full date format is specified as the parameter.

How to use pipes in templates:

To use a built-in pipe in an Angular template, the pipe name and any parameters are added after the data value is transformed. For example, to use the CurrencyPipe to format a number as a currency value, the following syntax can be used:

<!-- totalPrice is a number with the value of 1234.56 -->
<p> The total price is {{ totalPrice | currency:'USD':'symbol':'1.2-2' }} </p>

<!-- Output --> 
<!-- The total price is $1,234.56 -->

Here, the totalPrice variable is transformed using the CurrencyPipe and the USD currency code, currency symbol, and formatting options are specified as parameters. By default the symbol is true that is the reason '$' is present in the output. The format parameter 1.2-2 in the currency pipe specifies the precision and rounding of the formatted value.

The first digit (1 in this case) specifies the minimum integer digits that should be displayed. The second digit (2 in this case) specifies the minimum number of decimal digits that should be displayed.

The dash (-) before the second digit specifies the maximum number of decimal digits to be displayed after the decimal point. In this case, -2 means that up to 2 decimal places will be displayed after the decimal point, and any trailing zeros will be removed.

These were examples of pre-existing pipes in Angular and how to use them in your project. There are many other pipes provided by Angular that you can go ahead and explore on the web.

Custom Pipes in Angular

Angular also allows you to create your own custom pipes to format and transform data as per your needs. Custom pipes are essentially functions that can accept input values and transform them into output values using custom logic. Creating custom pipes can help you to write reusable code and reduce redundancy in your application.

Creating Custom Pipes

Creating a custom pipe in Angular is a straightforward process just kike you would create a service or a method in a component. You can create a new pipe using the ng generate pipe command, which will generate a new pipe with a default name and place it in the pipes folder of your application.

Once you have created your custom pipe, you can define your custom logic in the transform method of the pipe class. The transform method accepts the input value and any optional parameters and returns the output value after transforming it.

Here is an example of a custom pipe that reverses the order of a string:

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

@Pipe({ 
    name: 'reverse' 
}) 
exportclass ReversePipe implements PipeTransform { 
    transform(value: string): string { 
       returnvalue.split('').reverse().join(''); 
    } 
}

Implementing Custom Pipes in Angular

To use your custom pipe in Angular, you need to add it to the declarations array of the module where you want to use it. Once the pipe is added to the module, you can use it in your templates like any other built-in pipe.

Here's an example of using the custom reverse pipe in a template:

<p>Original: {{ message }}</p> 
<p>Reversed: {{ message | reverse }}</p>

Output:

Original: Hello World 
Reversed: dlroW olleH

Best Practices for Creating Custom Pipes

When creating custom pipes, it's important to follow some best practices to ensure that your code is maintainable and performs well. Here are some best practices to keep in mind:

  1. Keep your pipe simple and focused on a specific task.

  2. Avoid performing heavy computations or long-running operations inside your pipe.

  3. Use pure pipes whenever possible to avoid unnecessary re-evaluation of the pipe.

  4. Make sure to test your custom pipe thoroughly to ensure that it works as expected.

By following these best practices, you can create high-quality custom pipes that will help you to write better code and improve the performance of your Angular application.

Chaining Pipes in Angular

Chaining pipes in Angular allows you to apply multiple transformations to the same data in a specific order. Chaining pipes can be useful when you need to apply multiple formatting or transformation logic to a single value.

How to Chain Multiple Pipes

To chain multiple pipes in Angular, you can simply separate them using the | operator in your template. The order of the pipes is important, as the output of the first pipe will be passed as the input to the second pipe, and so on.

Here's an example of chaining the uppercase and date pipes to format a date value in uppercase:

<p>{{ birthday | date | uppercase }}</p>

In this example, the birthday value will first be formatted as a date using the date pipe, and then the output of the date pipe will be transformed to uppercase using the uppercase pipe.

Assuming that the birthday value is 1990-05-25, the output of the above code would be:

<p>MAY 25, 1990</p>

Examples of Using Multiple Pipes

Chaining pipes can be useful for a variety of use cases. For example, you can use the currency pipe and percent pipe to format a number as a currency value and a percentage value, respectively:

<p>{{ price | currency | percent }}</p>

In this example, the price value will first be formatted as a currency value using the currency pipe, and then the output of the currency pipe will be transformed into a percentage value using the percent pipe.

Assuming that the price value is 100, the output of the above code would be:

<p>10,000%</p>

Limitations of Chaining Pipes

While chaining pipes can be useful, it's important to keep in mind that using too many pipes can hurt the performance of your application. Each pipe adds an additional computation to the rendering process, and excessive use of pipes can cause the rendering process to slow down.

Additionally, chaining too many pipes can make your code harder to read and maintain. It's important to keep your code simple and focused on the task at hand and to avoid using too many pipes in a single template.

Thus, chaining pipes in Angular can be a powerful tool for formatting and transforming data, but it should be used judiciously to avoid performance issues and maintainability problems.

Conclusion

In conclusion, pipes are an important feature of Angular that allow developers to transform and format data easily in templates. The built-in pipes provide a wide range of formatting options for different types of data, while custom pipes can be created to meet specific formatting requirements. Chaining pipes can be useful, but it's important to consider the potential performance impacts of using too many pipes in a single expression. By following the best practices for creating and using pipes, developers can improve the readability and maintainability of their code, and create more intuitive and user-friendly interfaces for their applications.

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