deno

# Deno A JavaScript and TypeScript runtime with a package manager, formatter, linter, test runner, type checker, and bundler in one binary. Runs TypeScript directly. Needs Deno 2.9+. Check with `deno --version`, update with `deno upgrade`. ## Deno works the way npm and bun do Deno is not a separate ecosystem to port code into: - `deno install` reads an existing `package.json` and writes a real `node_modules`. - `deno add express` installs from **npm**. Unprefixed names default to npm. - `deno task build` runs `scripts.build` from `package.json` or `tasks.build` from `deno.json`. If both define it, `deno.json` wins. - Node built-ins work prefixed or not: `node:fs` and `fs` both resolve. - `deno main.js` runs a file. `deno run` is optional. - Deno reads `tsconfig.json`. Don't tell users to rewrite imports, adopt JSR, or restructure as a precondition. The two real differences are **permissions** and **npm lifecycle scripts not running by default**. Single-file scripts need no build step and no `tsconfig.json`. Applications and framework projects keep their normal setup. To convert an existing project, see the `migrate-to-deno` skill. ## Dependency management ```bash deno install # install everything declared deno add express # from npm (unprefixed = npm) deno add jsr:@std/path # from JSR deno add -D vitest # dev dependency (package.json only) deno remove express deno outdated # list outdated deps deno ...