Other Registries - Docs

There are several platforms besides JSR where you can share JavaScript libraries. In this section, we will highlight the distinctions between various options.

npm

npm is the primary and widely recognized platform for sharing JavaScript libraries. It was initially developed alongside Node.js in the early 2010s.

JSR is designed to complement npm, not replace it. JSR allows packages to reference npm packages using npm: specifiers.

JSR packages can also be used in tools that don’t yet natively support JSR, by using JSR’s npm compatibility layer.

We created JSR to address specific issues in the npm ecosystem:

Native TypeScript Support: JSR doesn’t require transpilation of TypeScript code before publishing. It’s explicitly built to support TypeScript features like “go-to-definition,” avoiding unnecessary encounters with declaration files (d.ts).
ESM Syntax: JSR promotes modern ECMAScript module (ESM) syntax over CommonJS, enabling simplified code structures.
Better Constraints: JSR enforces various constraints that enhance portability between Unix and Windows platforms, such as path length restrictions and disallowing certain file names.

deno.land/x

JSR and deno.land/x share common origins, but JSR is designed to be compatible with various runtimes and bundlers.

deno.land/x serves as a repository for hosting source code accessible via HTTPS. JSR was created to address several concerns related to deno.land/x:

Semver Enforcement: Deno.land/x does not enforce Semantic Versioning (semver), leading to challenges in deduplicating dependencies. Consequently, multiple versions of the same library may appear in the module graph.
Reliability: Deno.land/x lacks self-contained links, including links to potentially unreliable servers that may have gone offline since the code was published. This can undermine trust in the long-term reliability of deno.land/x libraries.
TypeScript Performance: While Deno and deno.land/x offer native TypeScript support, there are performance issues when using HTTPS modules from deno.land/x. The type checker may continue to analyze code beyond a user’s control, impacting performance.

esm.sh

Esm.sh is a platform that serves npm packages over HTTPS. Before Deno provided native npm support, this was the preferred method for including npm dependencies in Deno programs.

In contrast to esm.sh, JSR does not serve npm packages directly. JSR operates as an independent registry that allows npm dependencies while primarily focusing on pure JSR code.

Similarities with esm.sh:

ESM Modules Only: Both esm.sh and JSR exclusively provide ESM modules, not CommonJS.
Direct File Access: Like esm.sh, JSR offers direct access to individual package files via HTTPS.

unpkg.com

unpkg.com shares similarities with esm.sh by allowing access to individual files within npm modules over HTTPS. However, it provides fewer features compared to esm.sh.