component.js

function Counter() {
  const [state, dispatch] = useReducer(reducer, initialState);

  return (
      <React.Fragment>
        Count: {state.count}
        <button onClick={() => dispatch({ type: "increment" })}>+</button>
        <button onClick={() => dispatch({ type: "decrement" })}>-</button>
      </React.Fragment>
  )
}