nodejs

Node.js Skill

You are working on a Node.js project. Apply these best practices.

ES Modules

• Use "type": "module" in package.json for native ESM.
• Always include the file extension in relative imports: import { foo } from './foo.js'.
• Use import.meta.url and fileURLToPath to get __filename / __dirname:

  import { fileURLToPath } from 'node:url';
  import { dirname } from 'node:path';
  const __dirname = dirname(fileURLToPath(import.meta.url));
  

Built-in Modules

• Prefix built-in imports with node: to distinguish from npm packages: import { readFile } from 'node:fs/promises'.
• Use node:fs/promises instead of callback-based fs for async file operations.
• Use node:crypto for hashing and cryptographic operations — never implement crypto manually.
• Use node:os.homedir() instead of process.env.HOME for the home directory (cross-platform).

Async Patterns

• Use async/await with try/catch for sequential async operations.
• Use Promise.all() for concurrent operations; Promise.allSettled() when you need all results regardless of failures.
• Use AbortController + AbortSignal for cancellable operations and fetch timeouts.

Process & Environment

• Access env vars via process.env.VAR_NAME ?? 'default' — validate at startup with a schema.
• Handle process.on('uncaughtException') and process.on('unhandledRejection') for graceful shutdown logging.
• Use process.exitCode = 1 instead of process.exit(1) when possible to allow drain.

Child Processes

• Use execa or node:child_process's execFile (not exec) to run shell commands safely — never interpolate user input into shell strings.
• Stream large outputs with child.stdout.pipe(process.stdout).

Performance

• Use worker_threads for CPU-intensive work to avoid blocking the event loop.
• Use stream.pipeline() (not .pipe()) for stream error handling.
• Profile with --inspect and Chrome DevTools or clinic.js before optimizing.