What is yarn

Yarn is Yet Another Rackage Nanager: https://yarnpkg.com/

Claimed advantages over npm are speed, predictability, and offline capabilities.

Yarn basics

Install dependencies from package.json: npm install == yarn

Install a package and add to package.json: npm install package --save == yarn add package

Install a devDependency to package.json: npm install package --save-dev == yarn add package --dev

Remove a dependency from package.json: npm uninstall package --save == yarn remove package (note the --save param)

Upgrade a package to its latest version: npm update --save == yarn upgrade

Install a package globally: npm install package -g == yarn global add package

Cool things yarn can do

Show why a dependency was installed

yarn why package

serif@dig:~/dev/learn-something/02-learn-yarn$ yarn why simple-grep
yarn why v0.16.1
[1/4] Why do we have the module "simple-grep"...?
[2/4] Initialising dependency graph...
[3/4] Finding dependency...
[4/4] Calculating file sizes...
info Has been hoisted to "simple-grep"
info This module exists because its specified in "devDependencies".
info Disk size without dependencies: "12kB"
info Disk size with unique dependencies: "12kB"
info Disk size with transitive dependencies: "12kB"
info Amount of shared dependencies: 0

Update the version of the developed package

Shows the local package version from package.json, and asks for a new version number. Automatically updates package.json and commits the change.

yarn version

serif@dig:~/dev/learn-something/02-learn-yarn$ yarn version
yarn version v0.16.1
info Current version: 0.0.1
question New version:
error Invalid semver version
question New version: 0.0.2
info New version: 0.0.2
Done in 5.38s.

serif@dig:~/dev/learn-something/02-learn-yarn$ git log
commit 179394374ede8770f5d35aab0a003327b8f42715
Author: Bodnar Istvan <istvan.bodnar@kinja.com>
Date:   Sun Oct 23 17:26:26 2016 +0200

    v0.0.2

Dependency versions

Semver in npm: https://docs.npmjs.com/getting-started/semantic-versioning

Checker tool: https://docs.npmjs.com/misc/semver

Most used version ranges:

• ~ -- allows patch updates only (1.0.x)
• ^ -- allows minor and patch updates (1.x.y)
• >= -- use exact version or newer (x.y.z)

Note: public package versions has to start with 1.0.0!

Useful commands when working with versions

Set how version ranges are stored in package.json after yarn add

npm config set save-prefix='~'
# or
npm config set save-exact true

Install specific version:

npm install backbone@1.3.2
# or
yarn add backbone@1.3.2

Outdated packages

Check outdated dependencies, show their source and the latest available version number:

npm outdated
# or
yarn outdated

Use npm-update-outdated to update everything: https://www.npmjs.com/package/npm-update-outdated

Update-npm-packages as a service: https://greenkeeper.io/

Dependency types

devDependencies

Dependencies used only during development -- test runners, linters, formatters, etc.

npm install karma --save-dev
# or
yarn add karma --dev

peerDependencies

These won't be installed as dependencies, but rather mark the version of peers that will surely work with the local package. https://docs.npmjs.com/files/package.json#peerdependencies

bundledDependencies

Packages that are bundled when publishing the dependency. // TODO: what does that exactly mean?

optionalDependencies

These packages will be installed (TODO: dev, production?) -- and actually override versions in the dependencies section --, but if for any reason installation fails npm will still proceed. https://docs.npmjs.com/files/package.json#optionaldependencies

production dependencies

Install only packages required for production builds

npm install --production
# or
yarn --production

Setting the NODE_ENV env var can be used as well

NODE_ENV=production npm install

Missing from yarn

git+ssh:// links in dependencies

"devDependencies": {
  "simple-grep": "git+ssh://git@github.com:gawkermedia/simple-grep.git#master"
}

Workaround: replace host:path with host/path

"git+ssh://git@github.com/gawkermedia/simple-grep.git#master"

yarnpkg/yarn#513

xmas

npm xmas :((((((