JavaScript: Race condition in async operations

Quick fix

Read the commands before running them. Anything that restarts a service, deletes data or changes permissions should be tried on a non-production system first.

# Use Promise.all for parallel
const [result1, result2] = await Promise.all([
  promise1,
  promise2
]);
# Or sequential with await
const result1 = await promise1;
const result2 = await promise2;
# Add version/timestamp checks

How to diagnose JavaScript errors

JavaScript errors cluster into package management (resolution conflicts, lockfile drift, native build failures), asynchrony (unhandled rejections, race conditions, wrong this), and memory (the V8 heap limit, which is a fixed ceiling rather than a leak indicator on its own). Because JavaScript coerces rather than throws, many bugs surface far from their cause. undefined is not a function usually means a bad import, not a bad call.

If the quick fix above does not resolve it, work through these steps. They apply to this whole class of error, not just to this one message, which is usually what saves the time.

1. For dependency errors, read what npm actually reports as the conflicting peer requirement. Reaching for --force or --legacy-peer-deps installs a tree you have not validated.
2. Always attach a rejection handler: process.on('unhandledRejection', …) in Node, and check that every async function called from a non-async context has a .catch().
3. Raise the V8 heap only after confirming it is a genuine working-set problem: node --max-old-space-size=4096. If usage grows without bound, take a heap snapshot instead.
4. Use node --inspect with Chrome DevTools to take heap snapshots and compare allocations between two points in time.
5. For native module build failures (node-gyp), confirm Python and a C++ toolchain are present and that the Node major version matches the module's prebuilt binaries.

Tools worth reaching for

• node --inspect
• npm ls <pkg>
• node --max-old-space-size
• clinic.js
• why-is-node-running

Authoritative references

Primary documentation for this error, worth reading before applying any fix in production.

📖 developer.mozilla.org

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See all 42 JavaScript errors →

Browse other categories

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• Database 41Connections, deadlocks, constraints, replication and memory limits.
• AI 35Rate limits, context windows, GPU memory and model-serving failures.
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• Python 35Imports, virtual environments, encoding, concurrency and dependency conflicts.
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• Docker 27Daemon connectivity, disk space, image pulls, ports and architecture mismatches.
• System 26Disk space, systemd units, file descriptors, OOM killer and scheduled jobs.
• Cloud 25IAM permissions, quotas, service limits and credential failures.
• Security 25JWT validation, CSRF, OAuth grants, SELinux, SSH host keys and CSP.
• TLS 24Untrusted authorities, expiry, hostname mismatch, chains and cipher negotiation.
• Frontend 23Hydration mismatches, bundler resolution, layout shift and font loading.

Something missing or wrong?

This entry is maintained by hand. If the fix is out of date, incomplete, or you have a better one, email a correction and it will be reviewed.