Node.js® is a JavaScript runtime built on Chrome’s V8 JavaScript engine. Node.js uses an event-driven, non-blocking I/O model that makes it lightweight and efficient. Node.js’ package ecosystem, npm, is the largest ecosystem of open source libraries in the world.

node

Without argument it launches a JavaScript REPL

npm

The Node Package Manager npm can install packages in local or global mode.

In local mode it installs the package to the folder node_modules in the current working directory.

in global mode packages are installed to /usr/lib/node_modules/ which needs sudo.

Changing Location of Global Packages

Change the prefix to a folder in the HOME dir:

cd ~ && mkdir .node_modules_global
npm config set prefix=$HOME/.node_modules_global
$ cat .npmrc 
# prefix=/home/andre/.node_modules_global

Then reinstall npm and add new global bin dir to $PATH:

npm install npm --global
# add .bashrc
export PATH="$HOME/.node_modules_global/bin:$PATH"
which npm
# /home/sitepoint/.node_modules_global/bin/npm

Installing Packages in Global Mode

The Flag --global or just -g is used.

npm install uglify-js -g

Listing Global Packages

The installed packages with a full dependency graph are shown with

npm list -g

In order to see just packages we do:

npm list -g --depth=0

Installing Packages in Local Mode

For local installation a package.json file is used most of the time:

npm init

creates the file:

{
  "name": "project",
  "version": "1.0.0",
  "description": "",
  "main": "index.js"
}

It is modified when a new dependency is installed:

npm install underscore

{
  "dependencies": {
    "underscore": "^1.8.3"
  }
}