A Quick Introduction to the Yarn Package Manager

Introduction

Yarn is new and open source JavaScript package manager developed by Facebook. Yarn is fully compatible with the npm registry and can work alongside npm, but it’s aim it to be a safer, more secure and more reliable alternative.

You can replace your whole npm workflow with Yarn for new or current projects with very minimal effort. Dependencies in Yarn are kept in a yarn.lock file that should be checked-in your source control, but the file itself is for Yarn only and shouldn’t be edited. Here just enough to get your started with Yarn.

Installing the Yarn Package Manager

There are a few ways to install Yarn. You can, ironically enough, install it through npm:

npm install -g yarn

If you don’t have npm installed, you can also install with a simple bash script:

curl -o- -L https://yarnpkg.com/install.sh | bash

On Windows, you can get an installer file here.

Testing Your Yarn Installation

Run this to see if Yarn was properly installed or to see if you have the latest version:

yarn --version

Initializing a Yarn Project

To initialize a new project, run yarn init:

yarn init

Installing Yarn Dependencies

Here’s how to install all the dependencies from your package.json file (the equivalent of npm install):

yarn

Managing Yarn Dependencies

Let’s use lodash for most of our examples:

Adding a project dependency

Use the add command to add a dependency to your project:

yarn add lodash

You will see an output like this:

Output
yarn add v1.22.5
info No lockfile found.
[1/4] 🔍  Resolving packages...
[2/4] 🚚  Fetching packages...
[3/4] 🔗  Linking dependencies...
[4/4] 🔨  Building fresh packages...
success Saved lockfile.
success Saved 1 new dependency.
info Direct dependencies
└─ lodash@4.17.20
info All dependencies
└─ lodash@4.17.20
✨  Done in 1.48s.

Use the --dev (or its alias -D) flag to add a package as a dev dependency:

yarn add babel-cli -D

Updating a dependency

yarn upgrade lodash

or upgrade all the dependencies:

yarn upgrade

Removing a dependency

yarn remove lodash

Adding a global dependency

yarn global add lodash

Conclusion

This is a basic introduction to the Yarn Package Manager. Here are some other common commands:

• Get some information about a package: yarn info lodash
• Verify that the installed version of a package is a match between the package.json and the Yarn lock files: yarn check
• Publish a package: yarn publish
• Check for outdated packages: yarn outdated
• Find why a package is needed: yarn why lodash
• Run one of the scripts defined in package.json: yarn run test

Have fun with Yarn!