React - useCallback

useCallback is a React Hook that lets you cache a function definition between re-renders.

const cachedFn = useCallback(fn, dependencies)

Reference

import { useCallback } from 'react';

export default function ProductPage({ productId, referrer, theme }) {
  const handleSubmit = useCallback((orderDetails) => {
    post('/product/' + productId + '/buy', {
      referrer,
      orderDetails,
    });
  }, [productId, referrer]);