#React Generational Purify

A version of React's PureRenderMixin for functional components.

For more motivation, check out the React Advanced Performance Docs.

Usage

npm install react-generational-purify --save

const purify = require('react-generational-purify');

const PureFunComp = purify(props => <div>{props.foo}</div>);

The PureFunComp component will now skip rendering if the props and context have not changed.

Why Generational

Functional components are difficult to memoize because they do not have a this and you cannot tell the difference between different instances of the same component. An implementation of purify is to remember the props and context for the last render of each functional component. Then on the next render, you can skip rendering if the props and context have not changed. This implementation is limited if you have components with more than one instance on the page, e.g.:

const purify = require('react-generational-purify');
const Item = purify(props => <li>{props.position}</li>);

<ul>
  <Item position="first" key=0/>
  <Item position="second" key=1/>
</ul>

If different instances receive different props, the render method will never be skipped.

Another implementation of purify is to remember all combinations of props and context passed into render. This does skip rendering efficiently, but uses a lot of memory and can eventually crash the browser in many applications.

In the generational implementation, we keep track of all combinations of props and context that have been passed into render in the last generation. A generation is defined as a group of synchronous render calls. In the flux pattern, it is common to always re-render the top level component in your application. This will then synchronously render all children of the application, which eventually re-renders all instances of all components on the screen.

In the above example, if you render the ul, rendering Item with {position: "first"} and rendering Item with {position: "second"} will both be tracked. When you re-render the ul, it will know about both previous renders of Item and skip rendering on them. This will be true no matter how many times you render ul.

The net effect is that in each top-level render of your application, only the instances of components that have changed since the last top-level render will be rendered.