RFC: useForEach Hook

[pschiffmann]

In this RFC, I propose adding the useForEach Hook to React.

View RFC

Summary

The useForEach Hook provides a sane mechanism for calling React Hooks inside loops.

Basic example

The useForEach(keys, callback) Hook calls callback once for each element in the keys iterable.
The callback function is allowed to call Hooks, as if it was at the top level of the component.

import { useEffect, useForEach, useMemo, useState } from "react";

function MyComponent({ keys }) {
  const results = useForEach(keys, (key) => {
    const [state, setState] = useState(/* ... */);
    useEffect(/* ... */);
    return useMemo(/* ... */);
  });
  // ...
}

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[pschiffmann]

After writing the RFC, I had the idea to check for similar RFCs not just the open issues, but also the closed ones. (Genius, I know 😅) And I found #158 that seems to address the very same problem, just with a slightly different API.

I can see that #158 was closed because:

It is, in our opinion, a bit too complicated and advanced to be used widely, and not worth it if it's used rarely.

I know this is just a single data point, but at least for me and the type of apps I'm working on, this is a frequent real-world use case. So I'd be really happy if you could give this a second thought, or at least leave it open to see if it gathers more community interest.

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