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Pipes are used to transform a string, object, number and other values for display. They are very useful because it can be used directly in template or logic in all of our components.

Register pipe

Before we can use the pipes we need to register it in a component or in the module.

Here are the examples on how to register a pipe in component and in module.


In component
import { component, pipes, lowercase } from '@monster-js/core';

export function greeting() {
return <h1>{ 'Hello World!' | lowercase }</h1>

component(greeting, 'app-greeting');
pipes(greeting, lowercase);
In module
import { lowercase } from '@monster-js/core';
import { Module } from '@monster-js/core/module';

export const GreetingModule: Module = {
pipes: [lowercase]

Template pipes

In the template, we can use the pipes inside jsx expression container {}. The syntax is { <value> | <pipe selector> }.


<label>{ 'Hello World' | lowercase }</label>

In the example above, the lowercase is the pipe.


Template pipes may throw a typescript type checking error since the pipe operator is originally an arithmetic operator that accepts any, number and bigint values. A temporary fix for this is to set our values to type any. This error will be addressed in later releases.

Template pipes can also be chained to another pipe.


<label>{ 'Hello World 123' | lowercase | removeNumeric }</label>

In the example above, the lowercase pipe will run first and the removeNumeric pipe will run after the lowercase pipe.

Logic pipes

To use the pipe inside the component's logic we can just call the pipe function.


import { component, pipes } from '@monster-js/core';
import { lowercase } from './lowercase.pipe';

export function greeting() {

const message = lowercase('Hello World!');

return <h1>{message}</h1>

component(greeting, 'app-greeting');
pipes(greeting, lowercase);

Available pipes

Here are some usable pipes included in the core package.

lowercaseTransform string into lowercase.
uppercaseTransform string into uppercase.

Pipe with parameters

Pipes can also have one or more parameters to be used during transformation.

In template
<label>{ | date('YYYY-MM-DD', 'Invalid date')}</label>
In logic
import { Component, Pipes } from '@monster-js/core';
import { datePipe } from './date.pipe';

export function dateComponent() {

const date = datePipe(new Date(), ['YYYY-MM-DD', 'Invalid date']);

return <h1>{date}</h1>

component(dateComponent, 'app-greeting')
pipes(dateComponent, datePipe)