React Reffect

Create components whose prop changes map to a global side effect with the power of redux and new Context API.

!! This is a fork of react-side-effect, thanks to Dan Abramov for the awesome work!

Different from react-side-effect and the motivation of this project

When you use react-side-effect on server, you must call rewind() after every renderToString(), otherwise it will result a memory leak and incorrect results. However renderToString() is so heavy and blocks the node.js event loop.

React 16 supports Streaming to resolve this problem. You can use renderTo(Static)NodeStream instead of renderToString() and renderToStaticMarkup. Since it is an asynchronous api, thr non-thread-safe react-side-effect and rewind() will be broken and cause incorrect result.

This library use redux and React 16.3 new context API (use react-broadcast as a polyfill) to help you create a context for each request and prevent memory leak, so that you can use it safely both on server side and client side.

Installation

npm install --save react-reffect

Note: React Reffect requires React 15.3+.

As a script tag

Development

<script src="https://unpkg.com/react/umd/react.development.js" type="text/javascript"></script>
<script src="https://unpkg.com/react-reffect/lib/index.umd.js" type="text/javascript"></script>

Production

<script src="https://unpkg.com/react/umd/react.production.min.js" type="text/javascript"></script>
<script src="https://unpkg.com/react-reffect/lib/index.umd.min.js" type="text/javascript"></script>

Use Cases

• Setting document.body.style.margin or background color depending on current screen;
• Firing Flux actions using declarative API depending on current screen;
• Some crazy stuff I haven't thought about.

How's That Different from componentDidUpdate?

It gathers current props across the whole tree before passing them to side effect. For example, this allows you to create <BodyStyle style> component like this:

// RootComponent.js
import BodyStyle from './BodyStyle';
const store = BodyStyle.createStore();
return (
  <BodyStyle.Provider store={store}>
    <BodyStyle.Consumer style={{ backgroundColor: 'red' }}>
      {this.state.something ? <SomeComponent /> : <OtherComponent />}
    </BodyStyle.Consumer>
  </BodyStyle.Provider>
);

// SomeComponent.js
return (
  <BodyStyle.Consumer style={{ backgroundColor: this.state.color }}>
    <div>Choose color: <input valueLink={this.linkState('color')} /></div>
  </BodyStyle.Consumer>
);

and let the effect handler merge style from different level of nesting with innermost winning:

// BodyStyle.js
import { Component, Children } from 'react';
import PropTypes from 'prop-types';
import createSideEffect from 'react-reffect';

class BodyStyle extends Component {
  render() {
    return Children.only(this.props.children);
  }
}

BodyStyle.propTypes = {
  style: PropTypes.object.isRequired
};

function reducePropsToState(propsList) {
  var style = {};
  propsList.forEach(function (props) {
    Object.assign(style, props.style);
  });
  return style;
}

function handleStateChangeOnClient(style) {
  Object.assign(document.body.style, style);
}

export default createSideEffect(
  reducePropsToState,
  handleStateChangeOnClient
)(BodyStyle);

On the server, you’ll be able to call store.peek() to get the current state. The handleStateChangeOnClient will only be called on the client.

Migrate from react-side-effect

1. Change withSideEffect to createSideEffect and use { Consumer } instead of original result. Remove mapStateOnServer.

const BodyStyle = withSideEffect(
  reducePropsToState,
  handleStateChangeOnClient
)(BodyStyle);

export default BodyStyle;

to

const { Provider, Consumer, createStore } = withSideEffect(
  reducePropsToState,
  handleStateChangeOnClient
)(BodyStyle);

export default Consumer;
export const BodyStyleProvider = Provider;
export const createBodyStyleStore = createStore;

2. Wrap root component with Provider

const App = (
  <MyRootComponent />
);

to

const App = (
  <BodyStyleProvider>
    <MyRootComponent />
  </BodyStyleProvider>
);

3. Create a store both on server side and client side and use it with Provider. Make sure create a store for each request on server side.

const store = createBodyStyleStore();
const App = (
  <BodyStyleProvider store={store}>
    <MyRootComponent />
  </BodyStyleProvider>
);

4. Migrate mapStateOnServer and rewind()

const result = BodyStyle.rewind()

to

const result = mapStateOnServer(store.peek());

API

`createSideEffect: (reducePropsToState, handleStateChangeOnClient) -> ReactComponent -> {Provider, Consumer, createStore}

A helper to create Provider, Consumer and createStore. When mounting, unmounting or receiving new props on Consumer, calls reducePropsToState with props of each mounted instance. It is up to you to return some state aggregated from these props.

On the client, every time the returned component is (un)mounted or its props change, reducePropsToState will be called, and the recalculated state will be passed to handleStateChangeOnClient where you may use it to trigger a side effect.

On the server, handleStateChangeOnClient will not be called. You will still be able to call the static peek() method on the returned component class to retrieve the current state after a renderToString() call. Make sure to create a new store for each request, otherwise it will result in a memory leak and incorrect information.

Usage

Here's how to implement React Document Title (both client and server side) using React Reffect:

import React, { Children, Component } from 'react';
import PropTypes from 'prop-types';
import createSideEffect from 'react-reffect';

class DocumentTitle extends Component {
  render() {
    if (this.props.children) {
      return Children.only(this.props.children);
    } else {
      return null;
    }
  }
}

DocumentTitle.propTypes = {
  title: PropTypes.string.isRequired
};

function reducePropsToState(propsList) {
  var innermostProps = propsList[propsList.length - 1];
  if (innermostProps) {
    return innermostProps.title;
  }
}

function handleStateChangeOnClient(title) {
  document.title = title || '';
}

const SideEffect = createSideEffect(
  reducePropsToState,
  handleStateChangeOnClient
)(DocumentTitle);

export const createDocumentTitleStore = SideEffect.createStore;
export const DocumentTitleProvider = SideEffect.Provider;
export default SideEffect.Consumer;

LICENSE

MIT