Yarn is a software packaging system developed in 2016 by Facebook (now

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) for the

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runtime environment. An alternative to the

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package manager, Yarn was created as a collaboration of Facebook,

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(now Expo.dev),

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, and Tilde (the company behind

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) to solve consistency, security, and performance problems with large codebases.

Functionality

Users can write their own plugins for Yarn.

Constraints

Yarn constraints allow users to enforce rules for their dependencies or manifest fields across scoped workspaces.

Offline cache

Downloaded packages are cached and stored as a single file.

Plug'n'Play

Plug'n'Play allows users to run Node projects without node_modules folder, defining the way or location to resolve dependencies package files with the Plug-n-Play-control file. This feature is aimed to fix an unwell structured node_modules architecture and resulting in a faster Node.js application start-up time.

Plugins

Plugins can add new resolvers, fetchers, linkers, commands, and can also register to some events or be integrated with each other, most features of Yarn are implemented through plugins, including yarn add and yarn install'', which'' are also preinstalled plugins.

Protocols

Users can define which protocol will be used to resolve certain packages, for example, the ''git'' protocol is used for downloading a public package from a Git repository, and the ''patch'' protocol is used for creating a patched copy of the original package.

Release Workflow

Release Workflow automatically upgrades relative packages among monorepos workspaces when root packages are upgraded.

Workspaces

Workspaces allow multiple projects to work together in the same repository and automatically apply changes to other relatives when source code is modified, allowing installation of multiple packages by only running yarn installonce to install all of them in a single pass.

Zero-Installs

Zero-Installs solve the needs of installation of packages when packages is required to install when the codes is just fresh fetched to local.

Comparison to npm

* Yarn can install packages from local cache. * Yarn binds versions of the package strongly. * Yarn uses checksum for ensuring data integrity, while npm uses SHA-512 to check data integrity of the packages downloaded. * Yarn installs packages in parallel, while npm installs one package at a time.

References

{{Reflist JavaScript programming tools Package management systems