react-stateful-fn - Functional stateful components

• [x] setState on functional components
• [x] No need to bind your component methods
• [x] Optimized for performance
• [x] Zero dependencies
• [x] Extremely small: < 3kB

Installation

npm install react-stateful-fn
# or
yarn add react-stateful-fn

Usage

Let's have a look at everyone's favorite sample code: A simple counter widget.

import stateful from 'react-stateful-fn'

const increase = () => state => ({ clicks: state.clicks + 1 })

const Counter = (props, state, { setState }) => (
  <div>
    <div>Clicked {state.clicks} times</div>
    <button onClick={() => setState(increase())}>Increase +</button>
  </div>
)

export default stateful(Counter, { clicks: 0 })

As you can see, functional stateful components are good friends with functional setState.

We can do better

But if you care about performance you will probably not be completely happy with the previous example:

The button's onClick handler is an arrow function defined in the functional component. Thus it will be a different function on every render and will cause the button to re-render every time.

Let's fix that:

import stateful from 'react-stateful-fn'

const increase = () => state => ({ clicks: state.clicks + 1 })

const Counter = (props, state) => (
  <div>
    <div>Clicked {state.clicks} times</div>
    <button onClick={props.onClick}>Increase +</button>
  </div>
)

export default stateful(Counter, { clicks: 0 }, {
  onClick: event => ({ setState }) => setState(increase())
})

We can wire props and setState together outside the function, similar to Redux' connect(). The handlers defined there will be passed to the component as props.

If such a handler returns a function (as seen above) then this function is called with the { setState } object, so you can update the state according to the event.

Forms

Forms can be quite an elaborate business in React. Fortunately, stateful functional components turn out to be a convenient approach for easy form implementation.

import stateful from 'react-stateful-fn'

/**
 * Use as:
 *
 * <LoginForm onLogin={(email, password) => { ... }} />
 */
const LoginForm = (props, state) => (
  <form>
    <input type='email' placeholder='Email' value={state.email} onChange={props.onEmailChange} />
    <input type='password' placeholder='Password' value={state.password} onChange={props.onPasswordChange} />
    <button type='submit' onClick={props.onSubmitClick}>Login</button>
  </form>
)

const initialState = {
  email: '',
  password: ''
}

export default stateful(LoginForm, initialState, {
  onEmailChange: event => ({ setState }) => setState({ email: event.target.value }),
  onPasswordChange: event => ({ setState }) => setState({ password: event.target.value }),
  onSubmitClick: event => (_, props, state) => props.onLogin(state.email, state.password)
})

API

stateful(component: Function, initialState: ?Object, propHandlers: ?Object): Function

Make a functional stateless component stateful.

component

This is supposed to be a functional React component. You can use any ordinary functional component. The difference to a stateless component are the additional parameters.

The component will be called with the parameters (props: Object, state: Object, { setState: Function }).

initialState (optional)

Pass a custom initial state here. Otherwise it will default to {}.

propHandlers (optional)

Use propHandlers to pass stateful event handlers as props to the component. Useful to avoid arrow function event handlers which are considered bad practice.

If a property of propHandlers is not a function it will be added to the component's props as it is.

If a propHandlers handler returns a function this function will be called with the parameters ({ setState }, props, state).

License

MIT