JSR: The JavaScript Package Registry We've Been Waiting For

May 24, 2024Lev Gelfenbuim10 min. read

When speaking of JavaScript development, managing packages efficiently and securely has become a critical aspect of the developer's workflow. For years, npm has been the go-to package registry, powering millions of projects and helping developers share and reuse code. However, as the JavaScript ecosystem continues to grow and diversify, the limitations of npm and similar registries have become more apparent. The community has been longing for a solution that not only overcomes these limitations but also meets the evolving needs of JavaScript and TypeScript developers.

JSR (JavaScript Registry), the revolutionary package registry we've been waiting for. Designed with the future in mind, JSR offers a suite of features that enhance security, performance, and developer experience. It seamlessly integrates with existing tools and workflows while providing robust support for modern JavaScript standards like ECMAScript modules (ESM) and TypeScript.

The Evolution of JavaScript Package Management
Historical Context

JavaScript package management has come a long way since its early days. The introduction of npm (Node Package Manager) in 2010 revolutionized the way developers shared and reused code. Before npm, JavaScript developers had to manually manage dependencies, which was both time-consuming and error-prone. npm provided a centralized registry where developers could publish and discover packages, significantly boosting productivity and collaboration within the JavaScript community.

gmail-tester package on npmjs

Over the years, npm has grown exponentially, hosting millions of packages and becoming an indispensable tool for JavaScript development. However, as the ecosystem evolved, several limitations of npm became apparent. These include:

  1. CommonJS Limitation: npm was built around CommonJS, a module system that preceded the now-standard ECMAScript modules (ESM). This created compatibility issues, especially as the JavaScript community began adopting ESM​.
  2. Security Concerns: The centralized nature of npm has made it a target for supply chain attacks. Incidents like the left-pad fiasco highlighted the vulnerabilities in npm's ecosystem​.
  3. Performance Issues: As npm's registry grew, performance issues surfaced, particularly with dependency resolution and package installation times. Tools like Yarn and pnpm emerged to address these issues, but they also introduced additional complexity​.
Emergence of Modern Needs

The JavaScript landscape has continued to evolve, with new frameworks, tools, and runtime environments emerging. This evolution has introduced several new requirements and challenges:

  1. TypeScript Adoption: TypeScript, a statically typed superset of JavaScript, has gained widespread adoption. Developers need a package registry that natively supports TypeScript without requiring additional configuration or build steps​.
  2. Cross-Runtime Compatibility: With the advent of new JavaScript runtimes like Deno, Bun, and Cloudflare Workers, there is a need for a package registry that works seamlessly across these environments. A Node.js-centric registry like npm no longer meets the needs of the entire JavaScript ecosystem​.
  3. Improved Developer Experience: Modern developers expect tools that streamline their workflows and reduce boilerplate. Features like automatic documentation generation, secure publishing mechanisms, and integrated best practices are highly desirable​.
Why JSR is the Answer

JSR has been developed to address these modern needs and improve upon the limitations of existing package registries like npm. JSR focuses on:

  • Native TypeScript Support: JSR simplifies the use of TypeScript by automatically handling the generation of .d.ts files and API documentation from source code​.
  • ESM-Only Modules: By standardizing on ECMAScript modules, JSR ensures compatibility with the latest JavaScript standards and simplifies module loading across different environments​.
  • Cross-Runtime Compatibility: JSR supports a variety of JavaScript runtimes, making it a versatile choice for modern JavaScript development. This includes environments like Node.js, Deno, Next.js, and Cloudflare Workers​.
  • Enhanced Security and Performance: JSR employs a global CDN for fast package delivery, ensures immutability of published packages, and uses tokenless authentication for secure publishing​.

JSR is poised to become the package registry that the JavaScript community has been waiting for, addressing contemporary challenges and enhancing the overall developer experience.

What is JSR?
Introduction to JSR

JSR, which stands for JavaScript Registry, is a modern, open-source package registry designed specifically for JavaScript and TypeScript. Developed to address the evolving needs of the JavaScript ecosystem, JSR provides a streamlined, secure, and efficient way to manage and distribute JavaScript packages​.

Screenshot of https://jsr.io
JSR Key Features
  1. Native TypeScript Support: JSR is built with TypeScript in mind. When you publish a package to JSR, it handles the TypeScript source files directly, automatically generating API documentation and .d.ts files for type definitions. This eliminates the need for additional configuration or build steps, making it easier for developers to maintain TypeScript projects.
  2. ESM-Only Modules: In line with modern JavaScript standards, JSR uses ECMAScript modules (ESM) exclusively. ESM has become the standard for JavaScript modules, and JSR’s commitment to ESM ensures compatibility across various environments and simplifies the module loading process​.
  3. Cross-Runtime Compatibility: One of JSR’s standout features is its cross-runtime compatibility. It supports a variety of JavaScript runtimes, including Node.js, Deno, Bun, and Cloudflare Workers. This makes JSR a versatile choice for developers working in diverse environments. JSR modules can be used in any project that utilizes a node_modules folder, ensuring broad interoperability​.
  4. Seamless Integration with npm: JSR is designed as a superset of npm, not a replacement. This means that existing npm tools and workflows can be used with JSR without any disruption. Developers can continue to use npm, Yarn, or pnpm for package management, while benefiting from the additional features that JSR offers​.
  5. Enhanced Security and Performance Security and performance are top priorities for JSR. Packages published to JSR are immutable, which enhances security by preventing tampering. JSR also uses a global Content Delivery Network (CDN) to ensure fast and efficient package delivery. Furthermore, JSR’s tokenless authentication for publishing packages from CI (Continuous Integration) systems improves security and simplifies the publishing process​.

JSR aims to enhance the developer experience by providing tools and features that simplify package management and improve security. It represents a significant advancement in the way JavaScript and TypeScript packages are distributed and maintained, addressing many of the limitations found in traditional registries like npm.

Why JSR is the Registry We've Been Waiting For
Native TypeScript Support

JSR has been designed with native TypeScript support, making it a superior choice for modern JavaScript development. Unlike traditional registries that often require additional configuration and build steps to handle TypeScript, JSR automatically manages TypeScript source files. It generates .d.ts files for type definitions and comprehensive API documentation directly from the source code. This automation not only saves time but also ensures that TypeScript projects are easier to maintain and integrate with various tools and runtimes​.

ESM-Only Modules

One of the most significant advantages of JSR is its commitment to ECMAScript Modules (ESM). ESM has become the standard module format for JavaScript, replacing the older CommonJS format. By focusing exclusively on ESM, JSR aligns with the latest JavaScript standards, ensuring better performance, compatibility, and future-proofing for your projects. This focus on ESM simplifies the module loading process across different environments, providing a more consistent and reliable developer experience​.

Cross-Runtime Compatibility

JSR excels in cross-runtime compatibility, a crucial feature for today’s diverse JavaScript ecosystem. It supports multiple runtimes, including Node.js, Deno, Bun, and Cloudflare Workers. This means that developers can use JSR modules in various environments without worrying about compatibility issues. Whether you are working on a server-side application with Node.js, a serverless function with Cloudflare Workers, or a Deno-based project, JSR promises seamless integration and functionality across all these platforms​.

Seamless Integration with npm

JSR is not intended to replace npm but to enhance it. It acts as a superset of npm, meaning that it builds upon the functionalities of npm while adding new features and improvements. This seamless integration allows developers to continue using familiar npm-based tools and workflows. You can manage your packages with npm, Yarn, or pnpm and still benefit from JSR’s advanced features, such as automated documentation and enhanced security​.

Security and Performance Enhancements

Security and performance are critical aspects of JSR. The registry employs several measures to ensure that packages are delivered securely and efficiently:

  • Immutability: Once a package is published to JSR, it becomes immutable. This prevents any tampering or unauthorized modifications, ensuring that the code you depend on remains consistent and trustworthy​.
  • Global CDN: JSR uses a global Content Delivery Network (CDN) to distribute packages. This not only speeds up package downloads but also ensures high availability and reliability, regardless of where your users are located.
  • Tokenless Authentication: For publishing packages, JSR uses a secure, tokenless authentication method. This approach simplifies the publishing process while reducing the risk of security breaches commonly associated with token-based systems​.
Enhanced Developer Experience

JSR is designed to improve the overall developer experience. It offers several features aimed at making package management more efficient and user-friendly:

  • Easy Publishing: Publishing packages to JSR is straightforward and requires minimal configuration. The process is streamlined with a single command, and the CLI provides guidance throughout​.
  • Automatic Documentation: JSR automatically generates documentation from your TypeScript source code, ensuring that users have access to up-to-date and accurate information about your packages​.
  • Zero-Config GitHub Actions: For those using CI/CD pipelines, JSR supports zero-configuration publishing from GitHub Actions, making it easier to automate your workflows and ensure consistent releases​.

JSR addresses the modern needs of JavaScript development, providing a registry that is not only compatible with the latest standards but also enhances security, performance, and developer productivity. This makes JSR the registry the JavaScript community has been waiting for, offering a future-proof solution for package management.

By adopting JSR, developers can benefit from a more efficient, secure, and versatile package management experience, perfectly suited to the evolving landscape of JavaScript and TypeScript development.

How to Get Started with JSR
Using JSR Packages

Getting started with JSR is straightforward and can be done using your existing tools and workflows. Here’s a step-by-step guide on how to add and use JSR packages in your projects:

1. Adding a Package

To add a package from JSR to your project, you can use the following commands depending on the runtime you are using:


1deno add @luca/cases

npm (Node.js):

1npx jsr add @luca/cases

Alternatively, you can use yarn dlx, pnpm dlx, or bunx with the same syntax.

2. Importing and Using the Package

Once the package is added to your project, you can import it and use it in your JavaScript or TypeScript files. For example:

ES Modules:

1import { camelCase } from "@luca/cases";
3console.log(camelCase("hello world")); // "helloWorld"

Deno with JSR specifiers:

1import { camelCase } from "jsr:@luca/cases@1";
3console.log(camelCase("hello world")); // "helloWorld"

JSR packages are designed to work seamlessly with ES modules, making them easy to integrate into modern JavaScript projects.

Publishing to JSR

Publishing packages to JSR is designed to be simple and secure. Follow these steps to publish your JavaScript or TypeScript packages:

1. Write Your Code

Create your module in JavaScript or TypeScript. For example, a simple module might look like this:

2 * A module providing a function to greet people.
3 * @module
4 */
7 * Greet a person.
8 *
9 * @param name The name of the person to greet.
10 */
11export function greet(name: string) {
12  console.log(`Hello, ${name}!`);
2. Add a Configuration File

Create a jsr.json or deno.json file to define your package’s metadata, such as its name, version, and entry points.

2  "name": "@luca/greet",
3  "version": "1.0.0",
4  "exports": "./mod.ts"
3. Publish Your Package

Use the jsr publish or deno publish command to publish your package. The command will prompt you to authenticate and then proceed to publish your package.

1npx jsr publish

During the publishing process, you will be directed to authenticate through the JSR website, after which your package will be published and available on JSR.

@dbushell/xml-streamify package on jsr

JSR (JavaScript Registry) represents a significant step forward in the evolution of JavaScript package management. It addresses many of the limitations and challenges posed by traditional registries like npm, providing a modern, efficient, and secure solution tailored to the needs of today’s developers.

Summary of Benefits

JSR offers several key advantages:

  • Native TypeScript Support: Simplifies the use of TypeScript by automating the generation of .d.ts files and API documentation​.
  • ESM-Only Modules: Aligns with the latest JavaScript standards, ensuring better compatibility and performance​.
  • Cross-Runtime Compatibility: Works seamlessly across various JavaScript runtimes, including Node.js, Deno, Bun, and Cloudflare Workers, making it a versatile choice for modern development​.
  • Enhanced Security and Performance: Features like package immutability, global CDN distribution, and tokenless authentication ensure a secure and efficient package management experience​.
  • Improved Developer Experience: Offers easy publishing, automatic documentation, and zero-config GitHub Actions integration, helping developers streamline their workflows and focus on building great software​.

JSR is not just another package registry—it’s the JavaScript package registry we’ve been waiting for.

Article last update: May 24, 2024


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