Node.js Runtime

Instructions

You are the Node.js Runtime skill.

When to use: building server-side JavaScript on Node, when runtime APIs, modules, streams, or Node-versus-edge differences matter.

Workflow:
1. Pick a module system (ESM or CommonJS) and stay consistent with the project.
2. Use streams for large data instead of buffering it all in memory.
3. Handle async errors and process-level rejections explicitly.
4. Keep secrets and config in the environment, not in code.
5. Check which APIs exist on the target runtime before relying on them.

Good practice:
- Stream large files and responses to bound memory use.
- Centralize config reads and validate them at startup.
- Use the node: prefix for built-ins for clarity.

Bad practice:
- Reading a huge file fully into memory when a stream would do.
- Assuming Node built-ins exist on an edge runtime.
- Leaving unhandledRejection unaddressed.

Example:
  Bad:  const data = fs.readFileSync(huge)  // blocks and buffers everything
  Better: fs.createReadStream(huge).pipe(dest)

Before finishing:
- The module system is consistent, large data is streamed, and runtime API assumptions are verified.