Node.js

npm

Introduction#

Node Package Manager (npm) provides following two main functionalities: Online repositories for node.js packages/modules which are searchable on search.nodejs.org. Command line utility to install Node.js packages, do version management and dependency management of Node.js packages.

Syntax#

Parameters#

Parameter Example
access npm publish --access=public
bin npm bin -g
edit npm edit connect
help npm help init
init npm init
install npm install
link npm link
prune npm prune
publish npm publish ./
restart npm restart
start npm start
stop npm start
update npm update
version npm version
## Installing packages
# Introduction

Package is a term used by npm to denote tools that developers can use for their projects. This includes everything from libraries and frameworks such as jQuery and AngularJS to task runners such as Gulp.js. The packages will come in a folder typically called node_modules, which will also contain a package.json file. This file contains information regarding all the packages including any dependencies, which are additional modules needed to use a particular package.

Npm uses the command line to both install and manage packages, so users attempting to use npm should be familiar with basic commands on their operating system i.e.: traversing directories as well as being able to see the contents of directories.

Installing NPM

Note that in order to install packages, you must have NPM installed.

The recommended way to install NPM is to use one of the installers from the Node.js download page. You can check to see if you already have node.js installed by running either the npm -v or the npm version command.

After installing NPM via the Node.js installer, be sure to check for updates. This is because NPM gets updated more frequently than the Node.js installer. To check for updates run the following command:

npm install npm@latest -g

How to install packages

To install one or more packages use the following:

npm install <package-name>
# or
npm i <package-name>...

# e.g. to install lodash and express
npm install lodash express

Note: This will install the package in the directory that the command line is currently in, thus it is important to check whether the appropriate directory has been chosen

If you already have a package.json file in your current working directory and dependencies are defined in it, then npm install will automatically resolve and install all dependencies listed in the file. You can also use the shorthand version of the npm install command which is: npm i

If you want to install a specific version of a package use:

npm install <name>@<version>

# e.g. to install version 4.11.1 of the package lodash
npm install lodash@4.11.1

If you want to install a version which matches a specific version range use:

npm install <name>@<version range>

# e.g. to install a version which matches "version >= 4.10.1" and "version < 4.11.1"
# of the package lodash
npm install lodash@">=4.10.1 <4.11.1"

If you want to install the latest version use:

npm install <name>@latest

The above commands will search for packages in the central npm repository at npmjs.com. If you are not looking to install from the npm registry, other options are supported, such as:

# packages distributed as a tarball
npm install <tarball file>
npm install <tarball url>

# packages available locally
npm install <local path>

# packages available as a git repository
npm install <git remote url>

# packages available on GitHub
npm install <username>/<repository>

# packages available as gist (need a package.json)
npm install gist:<gist-id>

# packages from a specific repository
npm install --registry=https://myreg.mycompany.com <package name>

# packages from a related group of packages 
# See npm scope
npm install @<scope>/<name>(@<version>)

# Scoping is useful for separating private packages hosted on private registry from
# public ones by setting registry for specific scope
npm config set @mycompany:registry https://myreg.mycompany.com
npm install @mycompany/<package name>

Usually, modules will be installed locally in a folder named node_modules, which can be found in your current working directory. This is the directory require() will use to load modules in order to make them available to you.

If you already created a package.json file, you can use the --save (shorthand -S) option or one of its variants to automatically add the installed package to your package.json as a dependency. If someone else installs your package, npm will automatically read dependencies from the package.json file and install the listed versions. Note that you can still add and manage your dependencies by editing the file later, so it’s usually a good idea to keep track of dependencies, for example using:

npm install --save <name> # Install dependencies 
# or
npm install -S <name> # shortcut version --save 
# or
npm i -S <name>

In order to install packages and save them only if they are needed for development, not for running them, not if they are needed for the application to run, follow the following command:

npm install --save-dev <name> # Install dependencies for development purposes
# or
npm install -D <name> # shortcut version --save-dev
# or
npm i -D <name>

Installing dependencies

Some modules do not only provide a library for you to use, but they also provide one or more binaries which are intended to be used via the command line. Although you can still install those packages locally, it is often preferred to install them globally so the command-line tools can be enabled. In that case, npm will automatically link the binaries to appropriate paths (e.g. /usr/local/bin/<name>) so they can be used from the command line. To install a package globally, use:

npm install --global <name>
# or
npm install -g <name>
# or
npm i -g <name>

# e.g. to install the grunt command line tool
npm install -g grunt-cli

If you want to see a list of all the installed packages and their associated versions in the current workspace, use:

npm list
npm list <name>

Adding an optional name argument can check the version of a specific package.

Note: If you run into permission issues while trying to install an npm module globally, resist the temptation to issue a sudo npm install -g ... to overcome the issue. Granting third-party scripts to run on your system with elevated privileges is dangerous. The permission issue might mean that you have an issue with the way npm itself was installed. If you’re interested in installing Node in sandboxed user environments, you might want to try using nvm.

If you have build tools, or other development-only dependencies (e.g. Grunt), you might not want to have them bundled with the application you deploy. If that’s the case, you’ll want to have it as a development dependency, which is listed in the package.json under devDependencies. To install a package as a development-only dependency, use --save-dev (or -D).

npm install --save-dev <name> // Install development dependencies which is not included in production 
# or
npm install -D <name>

You will see that the package is then added to the devDependencies of your package.json.

To install dependencies of a downloaded/cloned node.js project, you can simply use

npm install
# or
npm i

npm will automatically read the dependencies from package.json and install them.

NPM Behind A Proxy Server

If your internet access is through a proxy server, you might need to modify npm install commands that access remote repositories. npm uses a configuration file which can be updated via command line:

npm config set

You can locate your proxy settings from your browser’s settings panel. Once you have obtained the proxy settings (server URL, port, username and password); you need to configure your npm configurations as follows.

$ npm config set proxy https://<username>:<password>@<proxy-server-url>:<port>
$ npm config set https-proxy https://<username>:<password>@<proxy-server-url>:<port>

username, password, port fields are optional. Once you have set these, your npm install, npm i -g etc. would work properly.

Scopes and repositories

# Set the repository for the scope "myscope"
npm config set @myscope:registry https://registry.corporation.com

# Login at a repository and associate it with the scope "myscope"
npm adduser --registry=https://registry.corporation.com --scope=@myscope

# Install a package "mylib" from the scope "myscope"
npm install @myscope/mylib

If the name of your own package starts with @myscope and the scope “myscope” is associated with a different repository, npm publish will upload your package to that repository instead.

You can also persist these settings in a .npmrc file:

@myscope:registry=https://registry.corporation.com
//registry.corporation.com/:_authToken=xxxxxxxx-xxxx-xxxx-xxxxxxxxxxxxxxx

This is useful when automating the build on a CI server f.e.

Uninstalling packages

To uninstall one or more locally installed packages, use:

npm uninstall <package name>

The uninstall command for npm has five aliases that can also be used:

npm remove <package name>
npm rm <package name>
npm r <package name>

npm unlink <package name>
npm un <package name>

If you would like to remove the package from the package.json file as part of the uninstallation, use the --save flag (shorthand: -S):

npm uninstall --save <package name>
npm uninstall -S <package name>

For a development dependency, use the --save-dev flag (shorthand: -D):

npm uninstall --save-dev <package name>
npm uninstall -D <package name>

For an optional dependency, use the --save-optional flag (shorthand: -O):

npm uninstall --save-optional <package name>
npm uninstall -O <package name>

For packages that are installed globally use the --global flag (shorthand: -g):

npm uninstall -g <package name>

Basic semantic versioning

Before publishing a package you have to version it. npm supports semantic versioning, this means there are patch, minor and major releases.

For example, if your package is at version 1.2.3 to change version you have to:

  1. patch release: npm version patch => 1.2.4
  2. minor release: npm version minor => 1.3.0
  3. major release: npm version major => 2.0.0

You can also specify a version directly with:

npm version 3.1.4 => 3.1.4

When you set a package version using one of the npm commands above, npm will modify the version field of the package.json file, commit it, and also create a new Git tag with the version prefixed with a “v”, as if you’ve issued the command:

git tag v3.1.4

Unlike other package managers like Bower, the npm registry doesn’t rely on Git tags being created for every version. But, if you like using tags, you should remember to push the newly created tag after bumping the package version:

git push origin master (to push the change to package.json)

git push origin v3.1.4 (to push the new tag)

Or you can do this in one swoop with:

git push origin master --tags

Setting up a package configuration

Node.js package configurations are contained in a file called package.json that you can find at the root of each project. You can setup a brand new configuration file by calling:

npm init

That will try to read the current working directory for Git repository information (if it exists) and environment variables to try and autocomplete some of the placeholder values for you. Otherwise, it will provide an input dialog for the basic options.

If you’d like to create a package.json with default values use:

npm init --yes
# or
npm init -y

If you’re creating a package.json for a project that you are not going to be publishing as an npm package (i.e. solely for the purpose of rounding up your dependencies), you can convey this intent in your package.json file:

  1. Optionally set the private property to true to prevent accidental publishing.
  2. Optionally set the license property to “UNLICENSED” to deny others the right to use your package.

To install a package and automatically save it to your package.json, use:

npm install --save <package>

The package and associated metadata (such as the package version) will appear in your dependencies. If you save if as a development dependency (using --save-dev), the package will instead appear in your devDependencies.

With this bare-bones package.json, you will encounter warning messages when installing or upgrading packages, telling you that you are missing a description and the repository field. While it is safe to ignore these messages, you can get rid of them by opening the package.json in any text editor and adding the following lines to the JSON object:

[...]
"description": "No description",
"repository": {
  "private": true
},
[...]

Publishing a package

First, make sure that you have configured your package (as said in https://stackoverflow.com/documentation/node.js/482/npm/2257/setting-up-a-package-configuration​). Then, you have to be logged in to npmjs.

If you already have a npm user

npm login

If you don’t have a user

npm adduser

To check that your user is registered in the current client

npm config ls

After that, when your package is ready to be published use

npm publish

And you are done.

If you need to publish a new version, ensure that you update your package version, as stated in https://stackoverflow.com/documentation/node.js/482/npm/2178/basic-semantic-versionini. Otherwise, npm will not let you publish the package.

{
    name: "package-name",
    version: "1.0.4"
}

Running scripts

You may define scripts in your package.json, for example:

{
  "name": "your-package",
  "version": "1.0.0",
  "description": "",
  "main": "index.js",
  "author": "",
  "license": "ISC",
  "dependencies": {},
  "devDependencies": {},
  "scripts": {
    "echo": "echo hello!"
  }
}

To run the echo script, run npm run echo from the command line. Arbitrary scripts, such as echo above, have to be be run with npm run <script name>. npm also has a number of official scripts that it runs at certain stages of the package’s life (like preinstall). See here for the entire overview of how npm handles script fields.

npm scripts are used most often for things like starting a server, building the project, and running tests. Here’s a more realistic example:

  "scripts": {
    "test": "mocha tests",
    "start": "pm2 start index.js"
  }

In the scripts entries, command-line programs like mocha will work when installed either globally or locally. If the command-line entry does not exist in the system PATH, npm will also check your locally installed packages.

If your scripts become very long, they can be split into parts, like this:

  "scripts": {
    "very-complex-command": "npm run chain-1 && npm run chain-2",
    "chain-1": "webpack",
    "chain-2": "node app.js"
  }

Removing extraneous packages

To remove extraneous packages (packages that are installed but not in dependency list) run the following command:

npm prune

To remove all dev packages add --production flag:

npm prune --production

More on it

Listing currently installed packages

To generate a list (tree view) of currently installed packages, use

npm list

ls, la and ll are aliases of list command. la and ll commands shows extended information like description and repository.

Options

The response format can be changed by passing options.

npm list --json
  • json - Shows information in json format
  • long - Shows extended information
  • parseable - Shows parseable list instead of tree
  • global - Shows globally installed packages
  • depth - Maximum display depth of dependency tree
  • dev/development - Shows devDependencies
  • prod/production - Shows dependencies

If you want, you can also go to the package’s home page.

npm home <package name>

Updating npm and packages

Since npm itself is a Node.js module, it can be updated using itself.

If OS is Windows must be running command prompt as Admin

npm install -g npm@latest

If you want to check for updated versions you can do:

npm outdated

In order to update a specific package:

npm update <package name>

This will update the package to the latest version according to the restrictions in package.json

In case you also want to lock the updated version in package.json:

npm update <package name> --save

Locking modules to specific versions

By default, npm installs the latest available version of modules according to each dependencies’ semantic version. This can be problematic if a module author doesn’t adhere to semver and introduces breaking changes in a module update, for example.

To lock down each dependencies’ version (and the versions of their dependencies, etc) to the specific version installed locally in the node_modules folder, use

npm shrinkwrap

This will then create a npm-shrinkwrap.json alongside your package.json which lists the specific versions of dependancies.

Setting up for globally installed packages

You can use npm install -g to install a package “globally.” This is typically done to install an executable that you can add to your path to run. For example:

npm install -g gulp-cli

If you update your path, you can call gulp directly.

On many OSes, npm install -g will attempt to write to a directory that your user may not be able to write to such as /usr/bin. You should not use sudo npm install in this case since there is a possible security risk of running arbitrary scripts with sudo and the root user may create directories in your home that you cannot write to which makes future installations more difficult.

You can tell npm where to install global modules to via your configuration file, ~/.npmrc. This is called the prefix which you can view with npm prefix.

prefix=~/.npm-global-modules

This will use the prefix whenever you run npm install -g. You can also use npm install --prefix ~/.npm-global-modules to set the prefix when you install. If the prefix is the same as your configuration, you don’t need to use -g.

In order to use the globally installed module, it needs to be on your path:

export PATH=$PATH:~/.npm-global-modules/bin

Now when you run npm install -g gulp-cli you will be able to use gulp.

Note: When you npm install (without -g) the prefix will be the directory with package.json or the current directory if none is found in the hierarchy. This also creates a directory node_modules/.bin that has the executables. If you want to use an executable that is specific to a project, it’s not necessary to use npm install -g. You can use the one in node_modules/.bin.

Linking projects for faster debugging and development

Building project dependencies can sometimes be a tedious task. Instead of publishing a package version to NPM and installing the dependency to test the changes, use npm link. npm link creates a symlink so the latest code can be tested in a local environment. This makes testing global tools and project dependencies easier by allowing the latest code run before making a published version.

Help text

NAME
       npm-link - Symlink a package folder

SYNOPSIS
         npm link (in package dir)
         npm link [<@scope>/]<pkg>[@<version>]

         alias: npm ln

Steps for linking project dependencies

When creating the dependency link, note that the package name is what is going to be referenced in the parent project.

  1. CD into a dependency directory (ex: cd ../my-dep)
  2. npm link
  3. CD into the project that is going to use the dependency
  4. npm link my-dep or if namespaced npm link @namespace/my-dep

Steps for linking a global tool

  1. CD into the project directory (ex: cd eslint-watch)
  2. npm link
  3. Use the tool
  4. esw --quiet

Problems that may arise

Linking projects can sometimes cause issues if the dependency or global tool is already installed. npm uninstall (-g) <pkg> and then running npm link normally resolves any issues that may arise.

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