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NodeJS Package Manager

Traditionally npm is used as package manager for NodeJS but you may also use yarn package manager which offered more speed till npm V5 (NodeJS 8). Within this book we mostly keep going with the default npm but both works the same.


But before you need the NodeJS system installed using the instructions on the website. It already comes with the NPM package manager.

Which version to use is based on the modules you want to run. But while NodeJS is mostly very good in backward compatibility also over major versions you should to go with the latest stable LTS (long term support) version.

Node version manager

For development systems you may test different versions so you may want to switch between versions on demand. This is possible using the nvm version manager. This allows you to try out your code in different versions and find problems.

Install it using the script:

curl -o- | bash

Then you may directly use it. It can install other versions and switch between versions easily.

Some of the commands are:

Command Usage
nvm current display currently activated version
nvm ls [<version>] list installed versions
nvm ls-remote [<version>] list versions available for install
nvm version <version> get best matching installed version
nvm version-remote <version> get best matching remote version
nvm install <version> download and install a version
nvm uninstall <version> uninstall a version
nvm use <version> modify path to use version
nvm which <version> show path there this version is installed

All node installations are done within the ~/.nvm directory.

If you detect that the module won't work with specific versions of node you should define the working versions in package.json.

Upgrade to new version

The following command will not only install a new version but also install all global modules which were installed in the current version.

$ nvm current
$ nvm version-remote 8
$ nvm install 8.1 --reinstall-packages-from=8.0
Downloading and installing node v8.1.0...
######################################################################## 100,0%
Computing checksum with sha256sum
Checksums matched!
Now using node v8.1.0 (npm v5.0.3)

Reinstalling global packages from v8.0.0...
+ flow-bin@0.47.0
added 9 packages and updated 1 package in 2.463s
Linking global packages from v8.0.0...

But after you changed your node version you should call npm install in your module again.


npm makes it easy for JavaScript developers to share and reuse code, and it makes it easy to update the code that you're sharing. npm is

  • a package manager for JavaScript
  • a free and open package repository

The npm package repository contains hundreds of thousands of packages. Which can be easily installed and included in your code.

NPM Installation

npm is bundled with NodeJS and installed with it. To update it to the newest version you may call:

sudo npm update -g npm

See the usage below.

New in npm 5

  • standardized lock-file package-lock.json is supported
  • --save is no longer necessary but --save-dev and --save-optional have to be used if needed
  • speeding up installation by using symlinks to centralized store
  • top level preinstall scripts now run before anything else
  • added prepack and postpack, which will not run on install only on publish
  • prepublishOnly now runs before the archive to publish is created
  • optimized output
  • lots of other fixes and optimization


Yarn is an alternative JavaScript package manager built by Facebook, Google, Exponent and Tilde. Yarn is only a new CLI client that fetches modules from the npm registry. But now with the upcoming npm 5 shipped with Node 8 the differences are smelting down.


In package.json, the file where both npm and Yarn keep track of the project’s dependencies, version numbers aren’t always exact. Instead, you can define a range of versions. This way you can choose a specific major and minor version of a package, but allow npm to install the latest patch that might fix some bugs.

In an ideal world of semantic versioning, patched releases won’t include any breaking changes. This, unfortunately, is not always true. The strategy employed by npm may result into two machines with the same package.json file, having different versions of a package installed, possibly introducing bugs.

To avoid package version mis-matches, an exact installed version is pinned down in a lock file. Every time a module is added, Yarn creates (or updates) a yarn.lock file. This way you can guarantee another machine installs the exact same package, while still having a range of allowed versions defined in package.json.

It is automatically working like npm with npm-shrinkwrap.json or npm since V5.

Parallel Installation

Whenever npm or Yarn needs to install a package, it carries out a series of tasks. In npm, these tasks are executed per package and sequentially, meaning it will wait for a package to be fully installed before moving on to the next. Yarn executes these tasks in parallel, increasing performance.

Cleaner Output

By default npm is very verbose. For example, it recursively lists all installed packages when running npm install <package>. Yarn on the other hand, isn’t verbose at all. When details can be obtained via other commands, it lists significantly less information with appropriate emojis.

Yarn Installation

Use npm to install yarn:

sudo npm install -g yarn

To update Yarn run the same call again.

Management Tasks

The following tasks are often needed and will be displayed how to do them in both. Other than some functional differences, Yarn also has different commands. Some npm commands were removed, others modified and a couple of interesting commands were added.

Install globally

# npm call
$ sudo npm install -g <package>
# yarn call
$ sudo yarn global add <package>

Unlike npm, where global operations are performed using the -g or --global flag, Yarn commands need to be prefixed with global.

Install Module

# npm call
$ npm install <package>
# npm befor v5 needs the save flag
$ npm install <package> --save
# yarn call
$ yarn add <package>

This will install dependencies from the package.json file and allows you to add new packages.

For development modules use:

# npm call
$ npm install <package> --save-dev
# yarn call
$ yarn add <package> --dev

Remove Package

# npm call
$ npm remove <package> --save
# yarn call
$ yarn remove <package>

This will remove the package and the dependencies from the package.json file.

Outdated packages

# npm call, first set the version in package.json
$ npm outdated
# yarn call, will ask for new version
$ yarn outdated

This will list the packages which are outdated.


Upgrade package

# npm call
$ npm update <package> --save
# yarn call
$ yarn upgrade <package>

This command upgrades packages to the latest version conforming to the version rules set in package.json (and recreates yarn.lock).

Interestingly, when specifying a package, it updates that package to latest release and updates the tag defined in package.json. This means this command might update packages to a new major release.

Upgrade interactive

# npm call
$ sudo npm install -g npm-check
$ npm-check -u
# yarn call
$ yarn upgrade-interactive

This tool allows you to interactively decide what to upgrade.

npm outdated

Run script

# npm call, the option -s is optional and suppress the mostly unwanted error hints
$ npm run <script> -s
# yarn call
$ yarn run <script>
# yarn alternative if script name not equal yarn commands
$ yarn <script>

You can run the scripts defined in package.json. With both you can call the binaries located in node_modules/.bin directly without prefixing this path.

NPM Login

# npm call, first set the version in package.json
$ npm login
# yarn call, will ask for new version
$ yarn login

Both will ask and store the credentials to access the npm package repository.


# npm call, first set the version in package.json
$ npm publish
# yarn call, will ask for new version
$ yarn publish


If you get a 404 error you may be not logged in, so please first log in.

npm ERR! code E404
npm ERR! 404 Not Found - PUT - Not found
npm ERR! 404 
npm ERR! 404  '@alinex/core@1.6.0' is not in the npm registry.
npm ERR! 404 You should bug the author to publish it (or use the name yourself!)

While npm published the package using the version from package.json, Yarn will interactively ask for it and update package.json for you.

You can also group packages in a scope (namespace). Each user has a scope with it's user or organization name. To publish something in this scope you have to use @<scope>/<name> and also need to add --access public because private packages are only valid for payed customers.

License Management

At the time of writing, no npm equivalent is available. yarn licenses ls lists the licenses of all installed packages. yarn licenses generate-disclaimer generates a disclaimer containing the contents of all licenses of all packages. Some licenses state that you must include the project’s license in your project, making this a rather useful tool to do that.

Yarn Analysis

This command peeks into the dependency graph and figures out why given package is installed in your project. Perhaps you explicitly added it, perhaps it’s a dependency of a package you installed. yarn why helps you figure that out.