Functional Web Components

Building Web Components with Functional Programming.

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Installation

Add to a lit project:

npm i @aggre/ullr

When creating a new project using lit as template and RxJS as the state management:

npm i @aggre/ullr lit rxjs

Partially supports run on Node.js (with jsdom).

APIs

shadow

shadow is a lit directive.

Encapsulate the template with Shadow DOM.

import { html } from 'lit'
import { shadow } from '@aggre/ullr'

export const main = (title: string, desc: string) =>
	shadow(html`
		<style>
			h1 {
				color: blue;
			}
		</style>
		<main>
			<h1>${title}</h1>
			<p>${desc}</p>
		</main>
	`)

Browser	Node.js
✅	🚸 Shadow Dom isn't supported. An inside content of Shadow Dom is shown as just an innerHTML.

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subscribe

subscribe is a lit directive.

Subscribe to Observable<T> of RxJS and re-rendering with the passed callback function.

When the directive part is removed or the passed observable is changed, the unused subscription will automatically unsubscribe.

import { html } from 'lit'
import { subscribe } from '@aggre/ullr'
import { timer as _timer } from 'rxjs'

export const timer = (initialDelay: number, period: number) =>
	subscribe(
		_timer(initialDelay, period),
		(x) => html` <p>${x}</p> `,
		html` <p>Default content</p> `,
	)

Browser	Node.js
✅	✅

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createCustomElements

createCustomElements creates a class that can be passed to customElements.define.

import { createCustomElements } from '@aggre/ullr'
import { main } from './main'

const observedAttributes = ['title', 'desc']

const template = ([title, desc]) => main(title, desc)

window.customElements.define(
	'x-app',
	createCustomElements(template, observedAttributes),
)

Browser	Node.js
✅	❌

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