What is JSR from Deno.js?

The open-source package registry for modern JavaScript and TypeScript. JSR is designed for TypeScript JSR packages are distributed as web-standard ECMAScript modules.

#Why is JSR?

JSR is a superset of NPM, much as TypeScript is a superset of JavaScript and was created to improve on the developer experience, performance,readability,and security of NPM.

#Native TypeScript support

JSR was designed with TypeScript support in mind. TypeScript, as a superset of JavaScript and test bed for the latest ECMAScript features, has emerged as a default choice for non-trivial JavaScript codebase.

#ECMAScript modules only

The web standard for JavaScript modules is ESM. A modern package registry should rally around this standard and shift the community in this direction.

#Cross-runtime support

JSR works with Deno and other NPM environments that populate a node_modules. This means that Node.js, Bun, Cloudflare Workers, and other projects that manage dependencies with a package.json can work together with JSR as well. Module authors can count on great editor support from strongly typed modules, without the need to transpile and distribute typings manually.

#Outstanding developer experience

• Easy publishing with a single command.
• Automatic API documentation generation.
• Zero-config publishing from GitHub Actions.
• Automatic inclusion of .d.ts files for Node.js/NPM distribution.
• Automated guidance on TypeScript best practices.

JSR is designed to be safe, quick, and adaptable, and also work well on devices with limited resources.

#Using JSR with Deno

you can add JSR imports using the Deno add command.

deno add jsr:@std/assert

You can then use the module from code like this.

#import * as _std_assert from "@std/assert";
import * as _std_assert from "jsr:@std/assert";

#Publish a JSR package

To create a JSR package, you need a mod.ts file in the root repo. The mod.ts tells about what to export.

// mod.ts
import * as chalk from "chalk";

import * as express from "npm:express@4";

After you have written your repo. you have to create a deno.json file. The file contains package metadata like name version and entrypoint(s).

// jsr.json / deno.json
{
  "name": "@luca/greet",
  "version": "1.0.0",
  "exports": "./mod.ts",
  ...
}

At last you you should run command deno publish to publish your package into the JSR.IO.

# deno
deno publish
# npm
npx jsr publish
# yarn
yarn dlx jsr publish
# pnpm
pnpm dlx jsr publish

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