Originally published at: http://www.sitepoint.com/beginners-guide-node-package-manager/
Node.js makes it possible to write applications in JavaScript on the server. It’s built on the V8 JavaScript runtime and written in C++ — so it’s fast. Originally, it was intended as a server environment for applications, but developers started using it to create tools to aid them in local task automation. Since then, a whole new ecosystem of Node based tools (such as Grunt and Gulp) has evolved to transform the face of front-end development .
To make use of these tools (or packages) in Node.js we need to be able to install and manage them in a useful way. This is where npm, the node package manager, comes in. It installs the packages you want to use and provides a useful interface to work with them. But before we can start using npm, we first have to install Node.js on our system.
Installing Node.js
Head to the Node.js download page and grab the version you need. There are Windows and Mac installers available, as well as pre-compiled Linux binaries and source code. For Linux, you can also install Node via the package manager, as is outlined here.
To verify that your installation was successful let’s give Node’s REPL a try.
$ node
> console.log('Node is running');
Node is running
> .help
.break Sometimes you get stuck, this gets you out
.clear Alias for .break
.exit Exit the repl
.help Show repl options
.load Load JS from a file into the REPL session
.save Save all evaluated commands in this REPL session to a file
> .exit
The Node.js installation worked, so we can now focus our attention on npm, which was included in the install.
$ npm -v 1.4.28
Node Packaged Modules
npm can install packages in local or global mode. In local mode it installs the package in a node_modules folder in your parent working directory. This location is owned by the current user. Global packages are installed in {prefix}/lib/node_modules/ which is owned by root (where {prefix} is usually /usr/ or /usr/local). This means you would have to use sudo to install packages globally, which could cause permission errors when resolving third-party dependencies, as well as being a security concern. Lets change that:
Changing the Location of Global Packages
Let’s see what output npm config gives us.
$ npm config list ; cli configs registry = "https://registry.npmjs.org/" user-agent = "npm/2.6.0 node/v0.10.36 linux x64" ; node bin location = /usr/local/bin/node ; cwd = /home/sitepoint ; HOME = /home/sitepoint ; 'npm config ls -l' to show all defaults.
This gives us information about our install. For now it’s important to get the current global location.
$ npm config get prefix /usr/local
This is the prefix we want to change, so as to install global packages in our home directory. To do that create a new directory in your home folder.
$ cd && mkdir .node_modules_global $ npm config set prefix=$HOME/.node_modules_global
With this simple configuration change, we have altered the location to which global Node packages are installed. This also creates a .npmrc file in our home directory.
$ npm config get prefix /home/sitepoint/.node_modules_global $ cat .npmrc prefix=/home/sitepoint/.node_modules_global
We still have npm installed in a location owned by root. But because we changed our global package location we can take advantage of that. We need to install npm again, but this time in the new user-owned location. This will also install the latest version of npm.
$ npm install npm --global npm@2.6.0 /home/sitepoint/.node_modules_global/lib/node_modules/npm
Finally, we need to add .node_modules_global/bin to our $PATH environment variable, so that we can run global packages from the command line. Do this by appending the following line to your .profile or .bash_profile and restarting your terminal.
export PATH="$HOME/.node_modules_global/bin:$PATH"
Now our .node_modules_global/bin will be found first and the correct version of npm will be used.
$ which npm /home/sitepoint/.node_modules_global/bin/npm $ npm -v 2.6.0