Once you find the right package, you'll be able to install it using the npm install command, as follows:

$ npm install <Package Unique Name>

Installing a module globally is similar to its local counterpart, but you'll have to add the –g flag, as follows:

$ npm install –g <Package Unique Name>

For example, to locally install Express, you'll need to navigate to your application folder and issue the following command:

$ npm install express

The preceding command will install the latest stable version of the Express package in your local node_modules folder. Furthermore, npm supports a wide range of semantic versioning. So, to install a specific version of a package, you can use the npm install command, as follows:

$ npm install <Package Unique Name>@<Package Version>

For instance, to install the second major version of the Express package, you'll need to issue the following command:

$ npm install [email protected] 

This will install the latest stable version of Express 2. Note that this syntax enables npm to download and install any minor version of Express 2. To learn more about the supported semantic versioning syntax, it is recommended that you visit https://github.com/npm/node-semver.

When a package has dependencies, npm will automatically resolve those dependencies, installing the required packages in a node_modules folder inside the package folder. In the preceding example, the Express dependencies will be installed under node_modules/express/node_modules.

To remove an installed package, you'll have to navigate to your application folder and run the following command:

$ npm uninstall < Package Unique Name>

npm will then look for the package and try to remove it from the local node_modules folder. To remove a global package, you'll need to use the -g flag, as follows:

$ npm uninstall –g < Package Unique Name>

To update a package to its latest version, issue the following command:

$ npm update < Package Unique Name>

npm will download and install the latest version of this package, even if it doesn't exist yet. To update a global package, use the following command:

$ npm update –g < Package Unique Name>

While you can manually create a package.json file, an easier approach would be to use the npm init command. To do so, use your command-line tool and issue the following command:

$ npm init

npm will ask you a few questions about your application and will automatically create a new package.json file for you. A sample process should look similar to the following screenshot:

Using npm init on Mac OS X

After creating your package.json file, you'll need to modify it and add a dependencies property. Your final package.json file should look like the following code snippet:

{
  "name": "mean",
  "version": "0.0.1",
  "description": "My First MEAN Application",
  "main": "server.js",
  "directories": {
    "test": "test"
  },
  "scripts": {
    "test": "echo \"Error: no test specified\" && exit 1"
  },
  "keywords": [
    "MongoDB",
    "Express",
    "Angular",
    "Node.js"
  ],
  "author": "Amos Haviv",
  "license": "MIT",
  "dependencies": {
    "express": "latest",
    "grunt": "latest"
  }
}

After creating your package.json file, you'll be able to install your application dependencies by navigating to your application's root folder and using the npm install command, as follows:

$ npm install

npm will automatically detect your package.json file and install all your application dependencies, placing them under a local node_modules folder. An alternative and sometimes better approach to installing your dependencies is to use the following npm update command:

$ npm update

This will install any missing packages and will update all of your existing dependencies to their specified version.

Another robust feature of the npm install command is the ability to install a new package and save the package information as a dependency in your package.json file. This can be accomplished using the --save optional flag when installing a specific package. For example, to install the latest version of Express and save it as a dependency, you can just use the following command:

$ npm install express --save

npm will install the latest version of Express and will add the Express package as a dependency to your package.json file. For clarity, in the upcoming chapters, we prefer to manually edit the package.json file. However, this useful feature can come in pretty handy in your daily development cycles.