useStream.js

import {useState, useEffect} from 'react';

/**
 * Resolve observable stream to value.
 *
 * @param stream - stream to resolve
 * @param initialValue - initial value to be immediately available
 */
export default (stream, initialValue) => {
  const [state, setState] = useState(initialValue);

  useEffect(() => {
    const listener = {
      next: setState,
    };

    stream.addListener(listener);
    return () => stream.removeListener(listener);
  }, []);

  return state;
};