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https://classic.yarnpkg.com/en/docs/Documentation for Yarn 1 (Classic), a fast, reliable, and secure package manager for JavaScript. Covers dependency management, .yarnrc configuration, offline mirrors, workspaces, selective version resolutions, and CLI commands such as yarn config and yarn version.
package.json file that describes the package.package.json files located in subfolders using a single root package.json. Key benefits include faster and lighter installations by preventing package duplication (hoisting) and automatic creation of symlinks between workspaces that depend on each other.Using Yarn as a package manager introduces a specific workflow for managing project dependencies. The core stages of this workflow include:
yarn.lock file in the project root to store the exact versions of every dependency installed. This ensures consistent and reproducible installs across different machines (e.g., local development and CI servers), providing more precision than the version ranges defined in package.json.yarn info <package> to retrieve metadata about a package in a tree format. The package does not need to be installed locally to fetch its information. By default, the output is a single-quoted serialization, but you can use the --json flag to emit valid JSON lines.# Get general info for react
yarn info react
# Get general info for react in JSON format
yarn info react --jsonYarn Classic provides several mechanisms to ensure fast and reliable dependency management:
Yarn Plug’n’Play (PnP) is an alternative installation strategy that replaces the traditional node_modules directory. Instead of relying on Node's default filesystem-based resolution (which recursively searches for node_modules folders), PnP generates a single .pnp.js file. This file acts as a map that tells Node exactly where to find each package in the dependency tree, eliminating the need for expensive I/O operations and filesystem queries during installation and runtime.
Key benefits of PnP include:
node_modules, which typically accounts for a majority of yarn install time.node_modules even if it isn't listed in package.json.stat and readdir syscalls Node must perform to resolve modules, speeding up application boot times.node_modules that hinder perfect hoisting and package sharing across projects.yarn.lock file to maintain consistency across different machines and environments. This file stores the exact versions of every installed dependency and their checksums. This prevents "Works On My Machine" problems and protects against accidental breaking changes in minor or patch versions of dependencies that follow Semantic Versioning (SemVer).Yarn manages project dependencies using two primary files: package.json and yarn.lock.
package.json: Used to declare all dependencies (development, production, and optional), specifying the package name and the minimum version required.yarn.lock: Ensures installation consistency across different environments by storing the exact versions of dependencies that were installed.Use the description, keywords, and license fields to provide information about your package for users and package managers.
License Requirements:
MIT).SEE LICENSE IN <filename> for non-standard licenses pointing to a file in the package root.UNLICENSED for private/unpublished packages where no rights are granted.{
"description": "My short description of my awesome package",
"keywords": ["short", "relevant", "keywords"],
"license": "MIT"
}cpu field specifies the CPU architectures the package is compatible with. Yarn validates this against process.arch. Use an array of allowed architectures or the ! prefix to exclude them.{
"cpu": ["x64", "ia32"],
"cpu": ["!arm", "!mips"]
}