react-side-effect

What is react-side-effect?

The react-side-effect package is a utility for creating higher-order components that handle side effects in React applications. It allows you to manage side effects in a declarative way, ensuring that they are handled consistently and predictably.

What are react-side-effect's main functionalities?

Creating a Side Effect Component

This feature allows you to create a higher-order component that manages side effects. The `reducePropsToState` function combines all props into a single state object, and the `handleStateChangeOnClient` function handles the side effect on the client.

const withSideEffect = require('react-side-effect');

function reducePropsToState(propsList) {
  // Combine all props into a single state object
  return propsList.reduce((acc, props) => ({ ...acc, ...props }), {});
}

function handleStateChangeOnClient(state) {
  // Handle the side effect on the client
  console.log('State changed:', state);
}

const SideEffectComponent = withSideEffect(reducePropsToState, handleStateChangeOnClient)(MyComponent);

Using the Side Effect Component

Once you have created the side effect component, you can use it in your React application like any other component. The side effects will be managed according to the logic defined in the higher-order component.

<SideEffectComponent prop1="value1" prop2="value2" />

Other packages similar to react-side-effect

react-helmet

react-helmet is a package that manages changes to the document head, such as title and meta tags, in a declarative way. It is similar to react-side-effect in that it handles side effects, but it is specifically focused on managing the document head.

redux-saga

redux-saga is a middleware library for managing side effects in Redux applications. It uses generator functions to handle asynchronous actions and side effects. While it is more complex than react-side-effect, it provides powerful tools for managing side effects in a Redux-based application.

react-use

react-use is a collection of React hooks that includes hooks for managing side effects, such as useEffectOnce and useAsync. It provides a more granular approach to managing side effects compared to react-side-effect, which focuses on higher-order components.

README

React Side Effect

Create components whose prop changes map to a global side effect.

Installation

npm install --save react-side-effect

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-side-effect/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-side-effect/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
return (
  <BodyStyle style={{ backgroundColor: 'red' }}>
    {this.state.something ? <SomeComponent /> : <OtherComponent />}
  </BodyStyle>
);

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

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

import { Component, Children } from 'react';
import PropTypes from 'prop-types';
import withSideEffect from 'react-side-effect';

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 withSideEffect(
  reducePropsToState,
  handleStateChangeOnClient
)(BodyStyle);

On the server, you’ll be able to call BodyStyle.peek() to get the current state, and BodyStyle.rewind() to reset for each next request. The handleStateChangeOnClient will only be called on the client.

API

withSideEffect: (reducePropsToState, handleStateChangeOnClient, [mapStateOnServer]) -> ReactComponent -> ReactComponent

A higher-order component that, when mounting, unmounting or receiving new props, 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 rewind() method on the returned component class to retrieve the current state after a renderToString() call. If you forget to call rewind() right after renderToString(), the internal instance stack will keep growing, resulting in a memory leak and incorrect information. You must call rewind() after every renderToString() call on the server.

For testing, you may use a static peek() method available on the returned component. It lets you get the current state without resetting the mounted instance stack. Don’t use it for anything other than testing.

Usage

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

import React, { Children, Component } from 'react';
import PropTypes from 'prop-types';
import withSideEffect from 'react-side-effect';

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 || '';
}

export default withSideEffect(
  reducePropsToState,
  handleStateChangeOnClient
)(DocumentTitle);