Yarn
Yarn is a fast, reliable, and secure package manager for JavaScript and Node.js projects, developed by Facebook. It manages project dependencies by downloading and installing packages from the npm registry or other sources, and it uses a lockfile to ensure consistent installs across different environments. It offers features like parallel downloads, offline caching, and deterministic dependency resolution to improve performance and reliability.
Developers should use Yarn for managing dependencies in JavaScript/Node.js projects when they need faster and more reliable package installations compared to npm, especially in large-scale applications or CI/CD pipelines. It's particularly useful for ensuring reproducible builds through its lockfile (yarn.lock) and for projects requiring offline capabilities or enhanced security with integrity checks. Yarn is also a good choice when working with monorepos using its workspaces feature.