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Dyo is a JavaScript library for building user interfaces.

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A JavaScript library for building user interfaces.

Coverage Size Licence NPM


  • Use a Direct Download: <script src=dyo.js></script>
  • Use a CDN: <script></script>
  • Use NPM: npm install dyo --save


Documentation can be find on the website.

See the Getting Started page for a quick overview.

The documentation is divided into several sections:

You can improve it by sending pull requests to this repository.


Several examples can be found on the website. Here's one to get started:

import {h, render} from 'dyo'

function Example (props) {
	return h('h1', {}, 'Hello ',

render(h(Example, {name: 'World'}), 'body')

This will render a heading element with the text content "Hello World" into the specified target(the body element).


The library is much alike React, so it's only natural that a comparison of the differences is in order; Which if successful might manage to highlight why it exists.


The Portal component supports string selectors as targets. This presents an array of different possibilities with regards to isomorphic target references.

function Example (props) {
	return h(Portal, {target: 'main'}, 'Hello')

render(h(Example), 'body')

In addition to this – re-parenting is baked into portals. That is when a portals container is changed, instead of unmounting its contents and re-mounting them to the newly designated container we can instead move its contents without replaying destruction unmount operations that may discard valuable interface and component state.

In co-ordination with custom renderers, portals afford the opportunity to create atomic branch specific custom renderers. Imagine isolated declarative canvas renderers within a document renderer.


Promises(or thenables) are first class values. This affords authors the ability to render promises, directly await promises within effects and events, and delay unmounting.

render(props => Promise.resolve('Hello'), 'body')

function Example (props) {
	useEffect(async () => {
		// out of band updates in here
		// are also batched
		return async () => {
			// delays unmount until the animation
			// has completed
			return props.current.animate({}).finished


In an async world, public interfaces like render are not guaranteed to complete synchronously if a subtree happens to have async dependencies within it. A consequence of this will see more use cases for the optional callback arguments that this function accepts – in much the same way authors are afforded the ability to await on this central routine.

await render(props => Promise.resolve('Hello'), 'body')

In addition to other hooks, a resource allocation hook that can be used to fetch and cache resources.

function Example (props) {
	const resource = useResource(props => fetch(''))
	return h('pre', {}, JSON.stringify(resource))
Async Server Rendering

Server side rendering supports the plethora of async primitives supported.

import {http} from 'http'
import {h, render, useResource} from 'dyo'

function Example (props) {
	const resource = useResource(props => fetch(''))
	return h('pre', {}, JSON.stringify(resource))

http.createServer((request, response) => {
	return render(h('html', {}, h(Example)), response)


Dyo is MIT licensed.