Skill

migrate-to-deno

Name: migrate-to-deno
Author: Deno

migrate Node.js projects to Deno

Published by Deno Updated Jul 31

Covers Deno Node.js TypeScript JavaScript Migration

Description

Use when moving a Node.js, npm, Yarn, pnpm, or Bun project to Deno, or when adopting Deno incrementally in an existing JavaScript or TypeScript codebase. Covers using Deno as a drop-in package manager, running existing package.json scripts, CommonJS versus ESM, node_modules layout, lockfile migration, permissions, whether to adopt the built-in toolchain, and per-tool command equivalents.

SKILL.md

Migrating to Deno

Requires Deno 2.9 or later. For general Deno usage once migrated, see the deno skill.

Most Node projects already run under Deno

Deno reads an existing package.json, resolves the same npm packages, writes a real node_modules, runs the same scripts, and supports node: built-ins. TypeScript runs with no build step.

There is usually no code to change — only which binary you invoke. Don't start by rewriting imports to jsr:, swapping dependencies for Deno-specific ones, or restructuring directories. Proposing that is the most common way this goes wrong.

Migrate in rungs

Each rung is independently useful and reversible. Stop wherever suits the project; plenty of teams stop at rung 1.

Rung 1 — Deno as the package manager only

deno install

Reads package.json, resolves the same dependencies, writes node_modules, and creates deno.lock — seeded from any existing package-lock.json, yarn.lock, bun.lock, or pnpm lockfile, so pins and integrity hashes carry over instead of drifting.

The app still runs under node; teammates are unaffected. Commit deno.lock once verified. To back out: delete deno.lock and node_modules, then npm install.

Rung 2 — Run it with Deno

deno run -A main.js      # or: deno -A main.js
deno task build          # runs scripts.build from package.json

Use -A here. The goal is confirming the program works, not designing a permission policy — changing both at once makes failures ambiguous.

Rung 3 — Tighten permissions

Replace -A with the narrowest set that works: run it, read what it asks for, grant exactly that.

deno run --allow-net=api.example.com --allow-read=./config --allow-env=PORT main.js

This buys something Node cannot offer, and is worth doing before deploying.

Rung 4 — Optionally, adopt the built-in toolchain

deno fmt for prettier, deno lint for eslint, deno test for jest or vitest, deno check for tsc, deno watch for nodemon, deno compile for pkg.

Optional, and usually not worth it for an existing project. These are not drop-in replacements; parity is incomplete, so this is a real migration, not a config change. A project happy with prettier, eslint, and vitest should keep them and use Deno as runtime and package manager only. Prefer the built-in tools for new projects. If you do move an existing one, go a tool at a time.

Command equivalents

Task	npm	Yarn	pnpm	Bun	Deno
Install all	`npm install`	`yarn install`	`pnpm install`	`bun install`	`deno install`
Add	`npm i <p>`	`yarn add <p>`	`pnpm add <p>`	`bun add <p>`	`deno add <p>`
Add dev	`npm i -D <p>`	`yarn add -D <p>`	`pnpm add -D <p>`	`bun add -d <p>`	`deno add -D <p>`
Remove	`npm uninstall <p>`	`yarn remove <p>`	`pnpm remove <p>`	`bun remove <p>`	`deno remove <p>`
CI install	`npm ci`	`yarn install --immutable`†	`pnpm i --frozen-lockfile`	`bun install --frozen-lockfile`	`deno ci`
Run script	`npm run <s>`	`yarn <s>`	`pnpm <s>`	`bun run <s>`	`deno task <s>`
Run binary	`npx <p>`	`yarn dlx <p>`	`pnpm dlx <p>`	`bunx <p>`	`dx <p>`
Outdated	`npm outdated`	`yarn outdated`‡	`pnpm outdated`	`bun outdated`	`deno outdated`
Audit	`npm audit`	`yarn npm audit`†	`pnpm audit`	`bun audit`	`deno audit`
Why	`npm ls <p>`	`yarn why <p>`	`pnpm why <p>`	`bun why <p>`	`deno why <p>`
Run a file	`node f.js`			`bun f.ts`	`deno f.ts`
Run TS	`ts-node f.ts`			`bun f.ts`	`deno f.ts`
Watch	`nodemon f.js`			`bun --watch f.ts`	`deno watch f.ts`
Format	prettier			prettier	`deno fmt`
Lint	eslint				`deno lint`
Test	jest, vitest			`bun test`	`deno test`
Coverage	nyc, c8				`deno coverage`
Type-check	`tsc --noEmit`			`tsc`	`deno check`
Bundle binary	pkg, nexe			`bun build --compile`	`deno compile`

† Yarn Berry (v2+) spelling. Yarn Classic (v1) uses yarn install --frozen-lockfile and yarn audit.

‡ Yarn Classic only — Berry removed yarn outdated.

dx is a separate binary installed alongside Deno, and an alias for deno x. It does not appear in the top-level deno --help output. Like npx, it runs the package with the sandbox disabled.

deno approve-scripts                              # interactive picker
deno install --allow-scripts=npm:better-sqlite3   # or name them directly

A tool cannot find files inside `node_modules`

Deno's layout is pnpm-style: real files in node_modules/.deno/, exposed via symlinks. Tools assuming npm's flat hoisted tree need:

{ "nodeModulesLinker": "hoisted" }

What has no Deno equivalent

Say so rather than improvising a workaround that won't hold:

Yarn Plug'n'Play. Deno creates a real node_modules; .pnp.cjs is unused and .yarnrc.yml resolver settings don't transfer.
yarn patch / pnpm patched dependencies. Vendor or fork.
overrides / resolutions. Pin via an import map entry instead.
Registry and resolver tuning in .npmrc / .yarnrc.yml.
Bun build features — macros, HTMLRewriter, HTML entrypoints.

Per-tool details

references/FROM_NPM.md — lockfile seeding, node_modules layout, overrides
references/FROM_YARN.md — Plug'n'Play, Berry vs Classic, workspaces
references/FROM_PNPM.md — pnpm-workspace.yaml, catalog:, patches
references/FROM_BUN.md — Bun API translation, bunfig.toml
references/NODE_APIS.md — node: built-ins, DENO_COMPAT, CJS/ESM

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