This hook makes it easy to see which prop changes are causing a component to re-render.

- useWhyDidYouUpdateKeys.tsx

/**
 * Prints out the keys that changed and their old and new values. Useful for deeply
 * nested objects.
 * Bare minimum Typescript annotations to pass compiling
 **/

import _ from 'lodash';
import { useEffect, useRef } from 'react';

const isObject = (v: any) => v && typeof v === 'object';

// Hook
function useWhyDidYouUpdateKeys(name: any, props: { [x: string]: any; }) {
  /**
   * Get a mutable ref object where we can store props ...
   * ... for comparison next time this hook runs.
   **/

  const previousProps: any = useRef();
  useEffect(() => {
    if (previousProps.current) {
      // Get all keys from previous and current props
      const allKeys = Object.keys({ ...previousProps.current, ...props });
      // Use this object to keep track of changed props
      const changesObj: any = {};
      // Iterate through keys
      allKeys.forEach((key) => {
        const prev = previousProps.current[key];
        const up = props[key];
        // If previous is different from current
        if (prev !== up) {
          // If both are objects, then create an array of objects out of the different properties
          // the top-level key is the name of the field thats different, and the values are
          // the old and new values of the key represented by 'from' and 'to', respectively.
          if (isObject(prev) && isObject(up)) {
            const diff: any = _.reduce(prev, (res: any[], v, k): any => (
              _.isEqual(v, up[k]) ? res : res.concat({ [k]: { from: v, to: up[k] } })
            ), []);
            // add each property to the changesObj
            diff.forEach((el: any) => {
              const k = Object.keys(el)[0];
              changesObj[k] = el[k];
            });
          } else {
            // If previous and updated props are not objects, 
            // add them directly to the changes objects in the same format
            changesObj[key] = {
              from: previousProps.current[key],
              to: props[key],
            };
          }
        }
      });
      // If changesObj not empty then output to console
      if (Object.keys(changesObj).length) {
        console.log('[why-did-you-update]', name, changesObj);
      }
    }
    // Finally update previousProps with current props for next hook call
    previousProps.current = props;
  });
}

MyComponent.tsx

interface Props {
  captions: string[];
  initialValues: FormValues;
  onSubmit: (values: ListForSaleFormValues) => void
}

const MyComponent = ({ captions = [], initialValues, onSubmit }: Props) => {
  /* include all props here, also values from hooks that might need to be optimized */
  useWhyDidYouUpdateKeys('MyComponent', { captions = [], initialValues, onSubmit });
  /* rest of the component.... */
};