yarn

Besides npm, there is another widely used node package manager called yarn.

Both of them are roughly equal in functionality. Initially, people choose yarn because it was better in the following ways:

Speed. Yarn caches every package it downloads so it never needs to download it again. It also parallelizes operations to maximize resource utilization so install times are faster than ever.
Security. Yarn uses checksums to verify the integrity of every installed package before its code is executed.
Version locking. Using a detailed, but concise, lockfile format, and a deterministic algorithm for installs, Yarn is able to guarantee that an install that worked on one system will work exactly the same way on any other system. No more 'works on my machine' problems!

Recently, npm has already caught up and there is no clear advantage of using yarn anymore. However, we still cover it here for your awareness.

Learning checklist

how to install yarn:
- mac: brew install yarn
- windows: choco install yarn
key yarn commands
- how to create a yarn project
  - yarn init
  - This creates a package.json file (our project configuration file)
- how to add packages with yarn (we will use cows npm package, just for good fun)
  - yarn add <package-name>
  - yarn add <package-name> --dev
- how to remove packages with yarn
  - yarn remove <package-name>
  - yarn remove <package-name> --dev
- how to add remove packages globally
  - yarn global add <package-name>
  - yarn global remove <package-name>
understand the mapping between yarn-npm
yarn.lock file
- don't modify yarn.lock file manually, run yarn upgrade to update the dependencies
- commit yarn.lock file into code repository

Let's try the npm package that we installed!

const cows = require("cows");

cow = cows()[0]; // try different array indexes (e.g. 1, 2, 3)

console.log(cow);