Migrate from Node.js

Deno 2 can run many existing Node projects. The goal is not to rewrite every import at once; it is to accumulate reversible compatibility evidence.

Incremental adoption

1. Pin Deno and record deno --version in the existing branch.
2. Keep package.json, the current lockfile, and the existing node_modules strategy; run one side-effect-free script first.
3. Execute current tests and classify failures in Node APIs, native addons, loaders, and lifecycle scripts.
4. Introduce deno.json tasks and run Deno commands beside current commands.
5. Remove old tools or lockfiles only after CI, developer, and production verification.

Compatibility conventions

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

Deno can also resolve common bare npm imports from package.json. Whether a local node_modules is enabled or required depends on project configuration and dependency behavior; one mode does not fit every package.

High-risk areas

• Node-API addons, postinstall scripts, and binary downloads;
• custom ESM loaders, resolution hacks, and implicit extensions;
• Jest/Vitest globals, fake timers, and snapshot differences;
• undeclared environment, filesystem, and network access;
• edge behavior in process, Buffer, streams, and Node APIs.

Official references: Node compatibility and Migrate to Deno.