vercel__next.js/examples/with-mobx/components/Clock.js

import { observer } from "mobx-react-lite";
import { useStore } from "./StoreProvider";

const Clock = observer(function Clock(props) {
  // use store from the store context
  const store = useStore();

  return (
    <div className={store.light ? "light" : ""}>
      {store.timeString}
      <style jsx>{`
        div {
          padding: 15px;
          color: #82fa58;
          display: inline-block;
          font:
            50px menlo,
            monaco,
            monospace;
          background-color: #000;
        }

        .light {
          background-color: #999;
        }
      `}</style>
    </div>
  );
});

export default Clock;