Pure function composition, no assignments.

react-hooks.js

const compose = (...fns) => x => fns.reduceRight((v, f) => f(v), x)


const useState = init =>
    ([init, (init => 
                    x => 
                        useState(init + x))(init)])

const createState = useState =>
          useState(3)

const render = ([count, setCount]) =>
   (`<div><p>${count}</p></div>
        <button onclick=${setCount}>My button</button>
        <div><p>${count}</p></div>`)


const component = useState => 
      compose(
        render,
        createState
      )(useState)

console.log(
  component(useState),
)


// "<div><p>3</p></div>"