Node.js Essentials Cheat Sheet

node --watch server.js

Restarts when the entry file or anything it imports changes.

node --env-file=.env server.js

Node 20.6 and up. Vars already in the shell win over the file.

node app.ts

Node 22.18 and 24 strip types by default. On an older 22 pass --experimental-strip-types. Type-only syntax runs; enums and parameter properties need --experimental-transform-types.

node --test

Finds *.test.js files. Write tests with import { test } from "node:test" and import assert from "node:assert/strict".

import { readFile } from "node:fs/promises";

const text = await readFile("notes.md", "utf8");

Leave off "utf8" and you get a Buffer.

const configPath = path.join(import.meta.dirname, "config.json");

Node 20.11 and up. Before that: path.dirname(fileURLToPath(import.meta.url)).

import { helper } from "./helper.js";

ESM imports need the file extension, even when the source file is .ts. Bare ./helper only works under a bundler.

import { execFile } from "node:child_process";
import { promisify } from "node:util";

const { stdout } = await promisify(execFile)("git", ["status", "--short"]);

execFile takes an argument array, so nothing in it goes through a shell.

process.exitCode = 1;

process.exit(1) cuts off pending stdout writes. Setting exitCode lets the event loop drain first.

const res = await fetch(url, { signal: AbortSignal.timeout(5000) });

Throws a TimeoutError after five seconds instead of hanging.

node --inspect-brk server.js

Open chrome://inspect in Chrome. Plain --inspect attaches without pausing.

console.time("query");
await db.query(sql);
console.timeEnd("query");

Prints query: 12.345ms. The label must match on both ends.