Angular Pipes

In Angular, pipes are a feature that allows you to transform the data before it's displayed on the view. Pipes take in data as input and return modified output to the view. You can use pipes to format numbers, currency, dates, and text, or to create your custom pipes.

Here's an example of how to use the built-in `date` pipe to format a date in an Angular template:

<p>The current date is {{ currentDate | date:'medium' }}</p>

In the example above, `currentDate` is a variable that contains a `date` object, and the date pipe is used to format the date in the "medium" format. The resulting output will look something like this:

The current date is Mar 29, 2023, 1:32:05 PM

Here's another example of using a custom pipe to filter a list of items based on a search term:

<!-- Component template -->
<input type="text" [(ngModel)]="searchTerm">
<ul>
  <li *ngFor="let item of items | filter:searchTerm">{{ item.name }}</li>
</ul>

In this example, we're binding an input element to the `searchTerm` variable using `ngModel`, and using a custom `filter` pipe to filter the `items` array based on the search term. The resulting output will be a list of items whose names match the search term.

To create a custom pipe, you need to create a TypeScript class with the `Pipe` decorator and implement the `transform` method. Here's an example of a custom pipe that takes in a string and returns the same string in uppercase:

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

@Pipe({ name: 'uppercase' })
export class UppercasePipe implements PipeTransform {
  transform(value: string): string {
    return value.toUpperCase();
  }
}

In the example above, we've created a `UppercasePipe` class that implements the `PipeTransform` interface and overrides the `transform` method to return the input string in uppercase. We've also decorated the class with the `Pipe` decorator and set its name to "uppercase".

To use this custom pipe in a template, you would use it like this:

<p>{{ 'hello world' | uppercase }}</p>

The resulting output would be:

HELLO WORLD

Overall, Angular Pipes is a great way to transform or format data before rendering in the template, however, overuse of Pipes may cause performance issues.

A video containing the process of generating pipes in Angular can be found here: