Packages

Built-in Node Packages

To know what we have access to with built-in node packages, we need to know what node version our environment is running in: - node --version - take a look at the docs: NodeJS Docs

• fs (file system) - reading and writing files
• path - manipulating file paths
• readline - reading data from somewhere else (like a file) line-by-line

Objects of Interest

• console - the console object
• process - the object representing the running program

For more information about these packages, see here: Built-in Node Packages. You will not be tested on this information for the assessment!!

Intro to npm

What is npm? - npm is a package manager that allows us to use bundled code written by other people and available on the npm online registry - it’s also a cli (command line) tool that we can use to interact with the npm online registry

root application folder - contains all your app’s files - includes npm requirements

package.json file - exists at the top of the root application folder - contains metadata - info about the project - contains scripts - commonly used commands in the project) - contains dependencies - other packages and their versions that your project relies on - safe to edit but be careful of using json syntax!

package-lock.json file - exists at the top of the root application folder - contains exact details about installed dependencies and their versions - represents an exact reproducible npm environment - do not edit!

node_modules folder - includes subdirectories for each dependencies - also includes dependencies of dependencies! Every package you need should be here - Don’t include in git version control system make sure to .gitignore this folder

npm Commands

• npm will show npm’s help info, including some common commands and how to access more detailed guides.

• npm init will set your current project directory up for npm. This requires answering a few questions to generate a package.json file, a critical part of npm’s dependency management functionality. (npm init --y will skip those questions and make a generic package.json for you.)

• npm install will download and install a package into your project. You can use the -g (or --global) flag to install a package for use everywhere on your system.
  • To have some fun, run npm install -g cowsay. Once the download’s completed, try running cowsay Hello, world!.

How npm installs packages

1. You request the package with npm install {PACKAGE NAME HERE}.
2. The npm CLI tool updates your package.json file to include the package as a dependency and requests the package from the npm registry.
3. npm downloads the package and installs it to the node_modulesfolder in your current directory (one will be created if it’s not already there). It chooses the most recent version by default.
4. npm creates a package-lock.json file that includes where the installed package is located and exactly which version was used.
5. You’re all set! You can now require('your-package-name-here'); anywhere in your project.

.gitignore

A .gitignore file allows us to tell git which files and directories to never include in our working directory and to never commit to our git logs.

The node_modules folder created by npm install contains massive amounts of files that we don’t want to be committing and tracking. - npm is a version-controlled package manager already so we don’t need to track changes to the code in the node_modules folder. - We only need to commit the versions of the packages we are using specified in the package.json and the package-lock.json files.

npm Lesson Learning Objectives

1. Explain what “npm” stands for.
2. Explain the purpose of the package.json file and node_modules directory.
3. Given multiple choices, identify the difference between npm’s package.json and package-lock.json files.
4. Use npm –version to check what version is currently installed and use npm to update itself to the latest version.
5. Use npm init to create a new package and npm install to add a package as a dependency. Then use require to import the module and utilize it in a JavaScript file.
6. Explain the difference between a dependency and a development dependency.
7. Given an existing GitHub repository, clone the repo and use npm to install it’s dependencies.