react-yjs

React hook for Yjs.

The hook automatically subscribes to changes in the Yjs data-structure and re-renders the component when the data changes. In addition it returns the result of the .toJSON from the Yjs data-structure.

npm install react-yjs

import { useY } from "react-yjs";

export const MyComponent = ({ yArray }) => {
  const names = useY(yArray)

  return (
    …
  )
}

Introduction Video (3:47min)

useY.Introduction.mov

Simple Usage

import { useY } from 'react-yjs';
import * as Y from 'yjs';

const yDoc = new Y.Doc();
const yNames = doc.getArray<string>('names');

export const MyComponent = () => {
  const names = useY(yNames);

  return (
    {names.map(name => <div>{name}</div>)}
  )
}

More Examples

Listening to a nested Yjs data-structure

const yDoc = new Y.Doc();
const yTodos = yDoc.getArray<Y.Map<string | boolean>>("todos");

// Any change of the todos (e.g. change checked) will trigger a re-render
const todos = useY(yTodos);

Change Todos:

// add a Todo
const todo = new Y.Map<string | boolean>();
todo.set("checked", false);
todo.set("text", newTodo);
yTodos.push([todo]);

// update the first Todo
yTodos.get(0).set("checked", true);

See the working example at https://react-yjs-example.vercel.app/. The code is available at examples/app/src/components/Todos.tsx.

Listening to a subset of a Yjs data-structure

const yDoc = new Y.Doc();
const yPosts = yDoc.getArray<Y.Map<string | Y.Array<string>>>("posts");
const yPost = new Y.Map<string | Y.Array<string>>();
yPosts.push([yPost]);
yPost.set("title", "Notes");
const yTags = new Y.Array<string>();
yTags.push(["cooking", "vegetables"]);
yPost.set("tags", yTags);

// Makes sure to listen only to changes of the tags of the first post
const yTagsOfFirstPost = yPosts.get(0).get("tags") as Y.Array<string>;
const tagsOfFirstPost = useY(yTagsOfFirstPost);

Remove a tag on the first post:

const tags = yPosts.get(0).get("tags") as Y.Array<string>;
tags.delete(index);

See the working example at https://react-yjs-example.vercel.app/. The code is available at examples/app/src/components/DeepStructure.tsx.

Architecture Decisions

The useY hook

The goals for this project are

trigger a re-render when the Yjs data changes
make use of useSyncExternalStore to avoid tearing
allow listening to a subset of the Yjs data-structure
allow listening to deeply nested data-structures
simple API

This resulted in creating a single hook that does a observeDeep the Yjs data-structure. This allows to expose one single hook to listen to deeply nested data-structures.

Still by passing in only a specific selector of a Yjs data-structure, the hook will only listen to that specific part of the data-structure.

Why not listen directly to the Y.Doc?

Yjs doesn't provide the APIs to do this on the Doc level. It would be possible to work around that, but sticking to the Yjs philosophy felt like a better option.

Types

The Yjs types could be much better yjs/yjs#614. Once this is release we can improve the types.

Sponsorship

Please contribute to the project financially - especially if your company relies on it. https://github.com/sponsors/nikgraf

License

The project is MIT licensed.

nikgraf / react-yjs