1. Node.js Packages Header Mastering Node.js, Part 4 Eric W. Greene
Microsoft Virtual Academy
Header
Mastering Node.js, Part 4
Node.js Packages
Eric W. Greene
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2. Course Overview Getting Started with Node.js Understanding Packages
Installing & Uninstalling Packages
Versioning & Outdated Packages
Global Packages & NPM Permissions
Updating & Configuring NPM
Developing & Publishing with Packages

3. Getting Started with Node.js
The course assumes some basic knowledge of Node.js and the JavaScript programming language
To run the examples on your machine, you will need Node.js installed
Node.js can be downloaded from here:
Install version 6 or later
If you do not understand the basics of these technologies, then watch the WintellectNOW courses, Introduction to Node.js and Node.js Modules

4. Node Package Manager (NPM)
Commonly referred to simply as NPM, the Node Package Manager is a package management system for the Node.js platform
Technically, NPM is not part of the Node.js project, but it is included along with Node.js in the official Node.js installer
NPM and Node.js follow different version number paths
Also, NPM is a for-profit corporation which provides the public package repository, and other private package hosting services

5. Node Package Manager (NPM)
De-facto standard package manager for Node.js applications and front-end web applications which use Node.js for development tooling
Lots useful tools such as Webpack, SASS, TypeScript, Babel, PhantomJS and lots more are distributed as NPM packages
NPM supports the distribution packages ranging from simple JavaScript-only packages to complex C++ based packages which require compilation when installed

6. Node Package Manager (NPM)
The public NPM package repository provides a web interface for searching for packages and exploring the details of packages
Additionally, the NPM web provides excellent documentation on how to use the NPM command line tool, including…
Installing/Uninstall Packages
Listing Package Dependencies
Checking for Outdated Packages
Developing with Packages

7. NPM Public Repository

8. Understanding Packages
Packages can be code libraries, applications or both
Typically, your projects themselves will be packages too
Packages do not have to be distributed via NPM, and do not have to be publicly available – but they can be if you want
A project is a package when it contains a package.json file

9. The package.json File
The package.json file contains metadata about the package including it's name, version, author, description, etc…
Additionally, a package.json contains the list of package dependencies that a package needs
Listing dependencies is one of the primary benefits of using a package.json file, allowing the package source code to be distributed independent of external packages

10. Creating a New Package
To create a new package, package.json file needs to creating and initialized in the folder where there package has been coded
When working with NPM the command line program npm is used
To initialized the package.json file, npm is invoked with the init command
The init command will prompt the developer with a series of questions concerning the name of the package, author, license, etc..
To skip the questions, and have a package.json file created instantly the –y option can be used

11. Creating a New Package

12. Installing / Uninstalling Packages
Creating a package.json file is not required to install and uninstall packages, but it is needed if you want to register installed packages as dependencies which can be easily installed again in the future when the project is deployed to another folder or system
Typically, packages are installed from the public repository, but it is possible to install packages from a repository local to your corporate network or even from linked packages local to your system
Setting up a corporate repository is beyond the scope of this course, but linked packages are discussed in Developing and Publishing Packages

13. Installing a Package
The command npm install <package-name> will install the specified package name
If the package should be registered as a production dependency of the package, the –S or –save flags should be specified
If the package should be registered as a development dependency of the package, the –D or –save-dev flags should be specified
If the package should be registered as an optional dependency of the package, the –O or –save-optional flags should be specified

14. Restoring Package Dependencies
When checking out a Node.js project with a package.json from source control, the node_modules folder is typically missing (generally node_modules is not committed source control)
To restore all dependencies, the command npm install with no package name should be used, NPM will read the package.json dependency configuration to restore the packages for the project
To restore only the dependencies for running the application in production (no development dependencies) run the npm install command with the --production flag

15. Peer Dependencies
Sets up a relationship between two packages where they are used together but are not dependent upon each other
Plugins are the best example, often plugins do not directly depend upon the package they plug into; therefore, they have cannot specify the version of the package they need
Peer dependencies allow packages to specify which host package its version that it is designed to work with
More Info:

16. Installing Scoped Packages
Scoped packages are associated with a particular organization
Scopes allow an organization's packages to be logically stored together
Works well for isolating private packages on NPM
When installing scoped packages, the scope is prefixed to the package name
All scoped packages are stored in a subfolder of the node_modules folder named after the scope

17. Installing From Other Sources
Most packages are installed from the public NPM repository, or a locally hosted NPM repository
Packages can be installed from other sources as well
Tarballs – local file or URL to a file
Git – including GitHub, BitBucket, GitLab and Gist

18. Uninstalling Packages
Packages can be installed using the npm uninstall <package name> command
Uninstalling packages removes all of its dependencies unless those dependencies are used by other packages not being uninstalled
To remove a saved dependency from the the package.json file when uninstalling packages include the same save flag as used when the package was installed

19. Installing and Uninstalling Packages

20. Versioning and Outdated Packages
NPM packages use the semver versioning system
Following the "spirit" of semver is the responsibility of the developer, and developers are greatly encouraged to do so
The versioning scheme use the following pattern:
MAJOR.MINOR.PATCH
So version would be a major version of '1', minor version of '2' and a patch version of '3'

21. Semantic Versioning

22. NPM Recommended Best Practices
Projects to be shared publicly should be initially released with a major version of 1
Bug fixes and other minor changes should be released as patch version increments
New features which do not break existing features should be released as minor version increment
Changes which are not backward compatible should be released as a major version increment
More:

23. Package Dependency Version Number
When installing and saving package dependencies, the version of the package is saved in the package.json file
Semver provides various patterns to determine what version of a package will satisfy the dependency requirement
The default version number scheme indicates that all versions up to, but not including, the next major version can be installed to meet the package dependency requirement
Exact version: 1.1.1

24. Patch, Minor & Major Increments
Patch increments up to but not including the next minor version:
1.2 – any 1.2 version up to but not including 1.3
1.2.x - any 1.2 version up to but not including 1.3
~1.2.3 – any version equal to or greater than up to but not including 1.3
Minor increments up to but not including the next major version:
1 – any version of 1 up to but not including 2
1.x – any version of 1 up to but not including 2
^ any version equal to or greater than up to but not including 2
Major increment "*" or "x" – up to latest version

25. Checking Outdated Packages
The command npm outdated will return a list of packages which are outdated, and could be upgraded
To check a specific package, execute npm outdated <package_name>
Current – is the current version of package which is installed
Wanted – is the highest version package which satisfies the semver version of the package in the package.json file
Latest – is the package version in the repository in the tagged with latest

26. Upgrading Packages
The command npm update will update all packages with a newer version within the range specified by the semver
Individual packages can be updated using npm update <package_name>
When npm update with no package name is used, missing packages will be installed
To save the new version numbers to package.json, use the –save and –save-dev flags

27. Updating Outdated Packages

28. Global Packages and NPM Permissions
In addition to installing packages within packages, package can also be installed globally
Installing packages globally on Mac and Linux requires super user permissions or adjusting folder settings for global packages
Either the global package folder needs to changed
Or the permissions of the default global package folder needs to be changed

29. Global Packages
The vast majority of package installations are local to a project
Global packages are primarily limited to executable programs – not code libraries
The recent trend has been to not install any packages globally, and instead install executable programs local to each project
Exceptions would be generator programs such as yeoman

30. Managing Global Packages
To install packages globally, the –g flag must be used when installing the package
To uninstall packages globall, the –g flag must be used when uninstalling the package
To see outdated global packages, use the –g flag when running the outdated command
To update global packages, use the –g flag when running the package update

31. Installing Packages Globally

32. Updating and Configuring NPM
NPM can update itself using the following command
npm update –g npm
NPM supports a number of configuration options
The most important options are for configuring proxy servers for downloading packages through a corporate firewall
npm config set proxy <some_url>
npm config set https-proxy <some_url>

33. NPM Configuration File
Setting configuration options will create a .npmrc file in the user's root folder
Project level configuration options can be set through an .npmrc file in the projects root folder
Global configuration options can be set in the $PREFIX/etc/npmrc file
$PREFIX can be determined by this command: npm config get prefix

34. NPM Configuration Commands
npm config set <key> <value> - sets a configuration value for the configuration key
npm config get <key> - gets a configuration value for the configuration key
npm config delete <key> - delete the configuration key and value
npm config list- list the configuration keys and values

35. Updating NPM and Setting the Configuration

36. Developing and Publishing
Packages are useful organizing larger projects, or sharing common code between different projects
NPM provides a linking feature which allows packages to be developed independently, yet executed together for debugging and testing purposes
Once developed, packages can be published to the NPM repository to be distributed to other projects
The company, npm, provides both the public repository (for free) and private repos (for a price) for distributing packages

37. Linking and Unlinking
To link two local packages to each other, the npm link command is used
To remove a link between two local packages, the npm unlink command is used
Each command accepts arguments depending upon the context of the linking and unlinking
Linking allows one local package to reference another local package similar to installing a package from the npm repository
This eases development and debugging of multiple packages

38. Linking Packages $ npm link
Creates a link to the current package folder from the global package folder
$ npm link some-package-name
Creates a link to the global package folder from the local package folder
$npm link folder-path-to-another-package
Create a link to the other package from the global package folder, then link to the global package folder from the current package folder
Allows linking to be in one step, instead of two

39. Linking Packages
Linking uses the specific operating system linking features on which npm is being executed
On Windows, the link is a directory junction (check out the mklink command)
On Mac and Linux, the link is a symbolic link (check out the ln command)

40. Unlinking Packages $ npm unlink
Removes the link to the current package folder from the global package folder
$ npm unlink some-package-name
Removes a link to the global package folder from the local package folder
unlink is an alias of the uninstall command

41. Linking and Unlinking Packages

42. Publishing Packages
The NPM public repository allows all JavaScript developers to publish the Node.js packages so that all developers can use them
To publish packages, an account is required
With a paid account, private packages can be published as well
NPM enterprise allows for local hosting of packages behind a corporate firewall

43. Publishing Packages
Once a package has been published, it should not be unpublished and removed from the repository
Unpublishing will break other which require the packages for completing their own package installs
There have been famous incidents of this happening with popular packages in the past
Instead of unpublishing, packages should be deprecated

44. Publishing Packages
Since publishing requires an account, the npm tool provides a login command which will log a user into NPM for publishing public and private packages
The login command is an alias for adduser
In addition to logging in, this command will create an account as well
Also, being logged in is required for install packages from private repositories
To logout, the npm logout command is used
To which account you are logged in with, use npm whoami
Naturally, this only works if you are logged in

45. NPM Account Creation

46. NPM Private Packages Repository

47. Publishing Packages

48. Conclusion NPM is the package manager for Node.js
NPM is a company, a package management standard and a public/private package distribution system
Projects are NPM packages if they contain a package.json file
Almost all projects should contain a package.json file so that external package dependencies can be tracked
NPM can be used to manage many aspects of your project setup including replacing the need for Gulp and Grunt