xferno

React hooks for infernojs.

Status: experimental. See the "How it works" note at the bottom of this readme.

Quick example

import { useState } from 'xferno';

function Counter() {
  const [count, setCount] = useState(0);

  return (
    <button onClick={() => setCount(count + 1)}>{count}</button>
  );
}

Installation

npm install --save xferno

Configuration

Be sure to modify your babel-plugin-inferno to have imports: 'xferno':

[
  "babel-plugin-inferno",
  {
    "imports": "xferno"
  }
]

Usage

The following "primitive" hooks are built into xferno. Custom hooks can be composed from these.

• useState
• useEffect
• useMemo
• useDisposable
• useSelector
• useDispatch

These each work similarly to the React equivalents. (Some of these have no React equivalents, though, so... keep reading.)

useState

import { useState } from 'xferno';

function Password() {
  // state can be a primitive for an object, etc. setState can be called
  // with a callback setState((s) => s) or with the new value for state
  // setState({ password: 'hoi' })
  const [state, setState] = useState({ password: '' });

  return (
    <input
      type="password"
      value={state.password}
      onInput={(e) => setState((s) => ({ ...s, password: e.target.value }))}
    />
  );
}

useEffect

useEffect can be called with no arguments, in which case it will be invoked only once for the entire life of the component. If it is given a second argument, the effect function will be invoked any time the second argument changes. If the effect function returns a function, that function will be invoked when the component is disposed or before the effect re-runs, which ever comes first.

import { useState, useEffect } from 'xferno';

function Clock() {
  const [time, setTime] = useState(new Date());

  useEffect(() => {
    let timeout = setTimeout(function tick() {
      setTime(new Date());
      timeout = setTimeout(tick, 1000);
    }, 1000);
    return () => clearTimeout(timeout);
  }, [setTime]);

  return (
    <h1>{time.toString()}</h1>
  );
}

useMemo

useMemo is used to memoize an expensive operation. If no second argument is passed, it will only run once (when the component first initializes) otherwise, it will re-evaluate any time the second argument changes.

import { useMemo } from 'xferno';

function Fanci(props) {
  const name = useMemo(() => {
    return reallyExpensiveCalculationFor(props.name);
  }, props.name);

  return (
    <h1>{name}</h1>
  );
}

useDisposable

useDisposable is like a combination of useEffect and useMemo. It allows the caller to return a value which can be consumed by the component, but also which is cleaned up any time the first argument is re-invoked or whenever the component is destroyed.

The first argument is a function which must return an object with a value property and a dispose function.

import { useDisposable } from 'xferno';

function Video(props) {
  const url = useDisposable(() => {
    const value = URL.createObjectURL(props.file);
    return {
      value,
      dispose: () => URL.revokeObjectURL(value),
    };
  }, props.file);

  return (
    <video src={url}></video>
  );
}

useSelector

useSelector provides a convenient mechanism for extracting a subset of Redux state for your component.

It is used in conjunction with Redux or a similarly shaped state store.

It is expected that context.store is a Redux (or similar) store, with dispatch, subscribe, and getState methods.

You can create your own component which provides this context, or you can use ReduxStoreProviderto provide it (as detailed further down).

import { useSelector } from 'xferno';

function Hello() {
  // Assuming we have Redux state that looks something like { name: 'World' }
  const name = useSelector((s) => s.name);

  return (
    <h1>Hello, {name}</h1>
  );
}

useDispatch

useDispatch provides the Redux dispatch function to your component.

This has the same requirements regarding Redux / store as useSelector.

import { useSelector, useDispatch } from 'xferno';

function ReduxCounter() {
  // Assuming we have Redux state that looks something like { count: 0 }
  const count = useSelector((s) => s.count);
  const dispatch = useDispatch();

  return (
    <button
      onClick={() => dispatch({ type: 'INC' })}
    >
      {count}
    </button>
  );
}

ReduxStoreProvider

If you want to use Redux (or something similar), you need to provide the Redux store to the useSelector and useDispatch hooks.

To do this, you can use ReduxStoreProvider somewhere near the root of your application.

import { ReduxStoreProvider } from 'xferno';

// ... reducer, initial state, etc omitted for brevity...

const store = createStore(reducer, initialValue);

function Main() {
  return (
    <ReduxStoreProvider store={store}>
      <OtherComponentsHere />
    </ReduxStoreProvider>
  );
}

How it works

This overrides inferno's createComponentVNode function and wraps all functional components in a hook-aware wrapper. The overriding of a core inferno function is what makes this an experimental library. This also modifies a global hook context in order to track hook state correctly across components. The level of hackery here means that more time and production-grade vetting is required before the experimental classification is removed.

Things that could use improving / adding:

• TypeScript definitions
• Better minification
• More intelligent hook state tracking
  • Right now, we wrap all functional components, but it would be far prefrable to somehow detect only those components that actually use hooks, and only wrap those.

License

MIT