Pipes in Angular

1. Introduction

Pipes in Angular are a powerful feature that allows you to transform data for display in your templates. They can be used to format dates, currencies, and other data types, enhancing the presentation of your application.

2. What are Pipes?

Pipes are simple functions that accept an input value and return a transformed value. They are used in Angular templates to format data for display. The syntax for using pipes is as follows:

{{ value | pipeName:argument1:argument2 }}

3. Built-in Pipes

Angular comes with several built-in pipes. Here are some commonly used ones:

• CurrencyPipe: Formats a number as currency.
• DatePipe: Formats a date value.
• DecimalPipe: Formats a number as decimal.
• JsonPipe: Converts an object into a JSON string.
• SlicePipe: Creates a new array or string containing a subset of the original items.

Code Example: Using Built-in Pipes

    
Price: {{ price | currency }}
    
Today: {{ today | date:'fullDate' }}

        

4. Creating Custom Pipes

Creating a custom pipe is straightforward. You need to implement the PipeTransform interface and decorate your class with the @Pipe decorator.

Step-by-Step Process to Create a Custom Pipe

1. Generate the pipe using Angular CLI.
2. Implement the PipeTransform interface.
3. Define the transform method to handle the input value.
4. Register the pipe in your module.

Code Example: Custom Pipe

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

@Pipe({
  name: 'exponential'
})
export class ExponentialPipe implements PipeTransform {
  transform(value: number, exponent: string): number {
    const exp = parseFloat(exponent);
    return Math.pow(value, isNaN(exp) ? 1 : exp);
  }
}
        

5. Best Practices

Here are some best practices when using pipes in Angular:

• Use pure pipes when possible to improve performance.
• Avoid complex logic in pipes; keep them simple.
• Use the async pipe for handling observables directly in the template.
• Test your pipes thoroughly to ensure they handle edge cases.

6. FAQ