Handling Partial Failures

The Problem

When processing a batch of items (like sending multiple emails or updating many records), a single failure often shouldn't crash the entire job. You need to know which items succeeded and which failed to generate a report.

The Solution

Combine batch processing with partitioning to separate successes from failures into two distinct lists.

async function processJob(items: string[]) {
  const results = await catchErrorAll(
      items.map(id => catchError(sendEmail(id)))
  );

  const { ok: sent, err: failed } = partition(results);

  console.log(`Successfully sent: ${sent.length}`);
  console.log(`Failed: ${failed.length}`);

  return { sent, failed };

}