Yarn

Yarn is package manager for JavaScript projects, but it solves some problems that the native npm exists.

Characteristic

Consistent Depedency Version

Yarn uses yarn.lock to lock the versions of the dependencies of packages. The reason of this is because package.json using by npm may using different version of dependencies, but Yarn always refers the version locked in yarn.lock.

Parallel Installation

The main reason convincing me to use Yarn instead of npm is this one. (As I think package-lock.json should locked the versions, too) Npm installs the packages sequentially, but Yarn installs in parallel. This greatly reduces the time used for installing packages.

Compatibility

Yarn depends on npm, except extra yarn.lock is added. The use of package.json is not affected, so it's available for switching from Yarn to npm.

Commands

Here only lists commands that are mostly used.

List commands

yarn help

Init New Project

yarn init

Install dependencies listed in package.json

yarn install

normally, this command updates yarn.lock.

with --frozen-lockfile flag, does not updates yarn.lock and ensures the version in different environment are same. Error will throw if the version between package.json and yarn.lock are not compatible.

with --offline flag, the installation does not use online resource (local cache instead), so it's even faster and only valid if the packages exist before and the command is run before.

Add dependencies...

yarn add [package]
yarn add [package]@[version]
yarn add [package]@[tag]

... for different environments

yarn add [package] --prod # prod dependencies, default
yarn add [package] --dev  # dev dependencies
yarn add [package] --peer # peer dependencies

Upgrade dependencies

yarn up [package]
yarn up [package]@[version]
yarn up [package]@[tag]

Remove dependencies

yarn remove [package]

Upgrade Yarn

yarn set version latest