How to Fix Generator Error in React

Running into a Generator Error in React? This guide walks you through the root cause and a practical fix.

Why This Happens

Generator errors in React happen when using function* or async function* incorrectly — missing the asterisk, forgetting yield, or trying to consume generator objects where arrays are expected.

How to Fix It

The key is to materialize generator values into an array with useMemo rather than using generators in JSX:

function* fibonacci() {
  let a = 0, b = 1;
  while (true) { yield a; [a, b] = [b, a + b]; }
}

function FibList({ count }) {
  const items = useMemo(() => {
    const gen = fibonacci();
    return Array.from({ length: count }, () => gen.next().value);
  }, [count]);

  return <ul>{items.map((n, i) => <li key={i}>{n}</li>)}</ul>;
}

Common Pitfall

One pitfall to avoid: applying a quick workaround that disables the underlying safety check. This masks the real problem and will come back to haunt you later. Consider adding a health check endpoint or startup validation that catches this misconfiguration before it reaches users.

Testing Your Changes

Run your test suite to make sure the fix doesn't introduce regressions. If you don't have tests covering this area, now is a good time to add a simple integration test. A quick manual smoke test across different browsers or environments can also catch edge cases your tests might miss.

Monitoring

Tip: Use [Bugsly](https://bugsly.dev) to automatically detect and alert you to React errors like this in production before your users notice them.