React bindings to mlyn

Usage no npm install needed!

<script type="module">
  import reactMlyn from '';



React bindings to mlyn

Goals of this library:

  • Reduce re-renders of the application due to subscription based model (update only components that changed).
  • Allow 2 way binding, without violating Unidirectional Data Flow.
  • Reduce react app / components boilerplate.
  • Reduce the amount of properties passed to components props / context, and make components reuse easier.


Install both react-mlyn and mlyn.

yarn add react-mlyn mlyn


npm i -S react-mlyn mlyn


Quick start

import Mlyn, { useSubject, seal } from "react-mlyn";

const App = seal(() => {
  const firstName$ = useSubject("Barbara");
  const lastName$ = useSubject("Radzivil");
  return (
      <div>First name:</div>
      <Mlyn.Input bindValue={firstName$} />
      <div>Last name:</div>
      <Mlyn.Input bindValue={lastName$} />
      <div>Full name:</div>
      <Mlyn.Div>{() => `${firstName$()} ${lastName$()}`}</Mlyn.Div>




Can show / hide an element on a condition, without re-rendering host component:

<Show when={() => subject() > 1}>
  {() => (
      <div>More than 1</div>


Used to display a collection of elements, by providing items to render and key extractor.

<For each={state$.todos} getKey={({ createdAt }) => createdAt}>
  {(todo$, index$) => (
      <Mlyn.Input type="checkbox" bindChecked={todo$.done} />
      <Mlyn.Input bindValue={todo$.title} />
      <button onClick={() => removeItem(index$())}>x</button>


useSubject: Creates a memoized subject, by passing to it initial state:

const subject = useSubject({ x: 1 });

useMlynEffect: Simlar to reacts useEffect, however doesn't require dependencies, cause it's automatically subscribed to to mlyn bindings. Please note, that invocation of hook callback doesn't mean that component has been re-rendered.

const usePersist = (key: string, subject: Sybject<any>) => {
    useEffect(() => {
        const persisted = localStorage.getItem(key);
        if (persisted) {
    }, []); // will perform once
    useMlynEffect(() => {
        localStorage.setItem(key, JSON.stringify(subject());

(Advanced) useSubjectValue: creates react state entry binded to the subject value. This hook will cause component re-render, which might can be required in components like For.

const subject = useSubject(0);
const value = useSubjectValue(subject); // starts with 0
useEffect(() => {
    // component will rerender
    // `value` will become 1
}, []);

Since subject has been invoked during execution of useMlynEffect callback, this callback will be reinvoked on every change of subject value.