Works like useState but for Class Components using this.setState

useThisState.js

function useThisState(key, component, initialState) {
	let set = (val) => component.setState({[key]: val}),
		initial = !(key in component.state)

	if (initial) {
		set(initialState)
	}

	let retVal = initial ? initialState : component.state[key]

	return [retVal, set]
}

// e.g. (from within a react class component)
// let [open, setOpen] = useThisState('open', this, false)