useWhyDidYouUpdate.js

// A copy-pasteable useWhyDidYouUpdate hook, adopted from the old & good usehooks.com (http://web.archive.org/web/20230203011511/https://usehooks.com/useWhyDidYouUpdate/).
//
// This hook will log whenever a component rerenders – and will print the props (or any other values
// you passed into it) that have changed between the rerenders.
//
// Usage:
//
// function MyComponent(props) {
//   useWhyDidYouUpdate('MyComponent', props)
//   
//   ...
// }
//
// Works with hooks and any other values as well:
//
// function MyComponent(props) {
//   const user = useSelector(userSelector)
//   const article = useSelector(articleSelector)
//
//   useWhyDidYouUpdate('MyComponent hooks', { user, article })
//   
//   ...
// }

function useWhyDidYouUpdate(name, props) {
  // Get a mutable ref object where we can store props ...
  // ... for comparison next time this hook runs.
  const previousProps = 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 = {};
      // Iterate through keys
      allKeys.forEach((key) => {
        // If previous is different from current
        if (previousProps.current[key] !== props[key]) {
          // Add to changesObj
          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;
  });
}