Use npm to Manage Node.js Packages

Node Package Manager, or NPM for short, is a command-line tool for installing and managing different node programs and Javascript packages, such as Angular.js, Express.js, and many others. NPM has many different tools for maintaining your Node.js environment. This guide will cover many of these tools, and demonstrate how to install and use these packages.

Prerequisites

Before using this guide, make sure that have both Node.js and npm installed on your server. If you do not have Node.js and npm installed, follow the install instructions for Node.js and npm in the Node.js install guide.

Basic NPM commands

  • For a list of subcommands:
    npm help
    Usage: npm command

    where command is one of:

        add-user, adduser, apihelp, author, bin, bugs, c, cache,
        completion, config, ddp, dedupe, deprecate, docs, edit,
        explore, faq, find, find-dupes, get, help, help-search,
    . . .
  • For a brief summary of what each command does:
    npm -l
    Usage: npm command

    where command is one of:

       adduser   npm adduser
                 Then enter stuff at the prompts.

       bin       npm bin
                 npm bin -g
                (just prints the bin folder)

    . . .
  • For a more detailed overview of each command:
    npm help subcommand
  • If you're unsure which command performs the action you want to perform, you may also search within the help topics:
    npm help-search search_term

System information

Now that npm is set up, and you know how to access the help file, we can start exploring. We'll start by learning how to ask for information about our system that relates to npm, but before we do, let's discuss the difference of Local Packages vs Global Packages.

Local vs global packages

When you create a Node.js application, you also create a directory structure that contains your application. In this structure there is a subdirectory called node_modules. This directory contains all the modules that can be locally installed.

  • Make an empty directory structure that will serve as your package directory. For example:
    mkdir -p ~/projects/test_package/node_modules
  • Navigate to the directory you just created:
    cd ~/projects/test_package

Note: You can use the regular Javascript require () method to use locally installed modules. In most cases, that's what you need for a package.

If you require command line capabilities for a package, you should install that package globally. Globally installed applications are stored inside the ~/.npm/ directory. Their commands will work in all Node.js applications on the server. However, globally installed packages can't be used with Javascript require ().

By default the majority of npm commands will assume you are referring to local packages. If you're not referring to a local package, you would use the -g or --global flags.

List installed packages

  • List local packages in our test directory:
    npm ls
    /home/demouser/projects/test_package
    └── (empty)

    npm ls will show as empty since we haven't installed any Node.js packages yet. However, npm will install some packages globally by default.

  • Use the -g flag to see those packages:
    npm ls -g
    /home/demouser/.nvm/v0.11.13/lib
      └─┬ npm@1.4.9
        ├── abbrev@1.0.4
        ├── ansi@0.2.1
        ├── ansicolors@0.3.2
        ├── ansistyles@0.1.3
        ├── archy@0.0.2
    . . .

    As seen above, there are quite a few global packages. There are other options you can use to modify the output. For example, you can use the -l or -a flags to show additional information.

Listing other information

  • Aside from installed packages, we can query npm about other information:
    npm root
    npm root should display the following output:
    /home/demouser/projects/test_package/node_modules
  • List the top-level path for the package you're working on:
    npm prefix
    /home/demouser/projects/test_package

    Note: You can also use the -g flag to see where the global files are being stored.

  • Use npm bin to list where npm installs its executables:
    npm bin
    npm bin should display the following output:
    /home/demouser/projects/test_package/node_modules/.bin

Exploring a package's files

  • By using the explore subcommand, you can quickly go to the directory where your package is installed:
    npm explore -g npm
    Exploring /home/demouser/.nvm/v0.11.13/lib/node_modules/npm

    When you're finished you can type 'exit' or ^D.

  • Exit when you're finished:
    exit

Search for packages

To locate a Node.js package, you can simply search for it using npm. For example, if we needed the express package for our project (Express.js is a web framework), we can search for that package in the npm package archives. These archives are located on the npm website.

  • Use npm to search for express.
    npm search express

    Note: Because this will generate a very long list, it's best to pipe it into less to make it easier to view.

  • Another way to do it is by using a regular expression:
    npm search /^express\[\ \]
    NAME      DESCRIPTION                               AUTHOR DATE VERSION
    express   Sinatra inspiblue web development framework =tjholowaychuk… 2014-05-12 4.2.0

    Note: If you receive too many results, it may be easier to go to the npm website. to find the name of the package. After you know the name of the package, you can install it.

  • Because we need command line functionality, we will install express globally:
    npm install -g express

    This downloads and also installs the express package as well as all of its dependencies inside the global npm root directory.

  • If you need the package in your local application's module directory so it can be included within the app with a require() line:
    cd ~/projects/test_package
    npm install express

Uninstall, de-duplicate, prune, and link packages

Because we want the package in our global and local scope, we will need to give it a way to have the package available in both locations.

  • For example, we can uninstall our local version of the package:
    npm uninstall express
  • We can tell npm that we want to link our global copy of the local package:
    npm link express

    This creates a symbolic link in our node_modules directory that points to our global package which makes it available in both locations. You can also do the reverse of this by uninstalling the global version, then going into the local package and linking it globally.

  • Uninstall the local link and global package:
    npm uninstall express # This removes the symbolic link in local npm uninstall -g express # This removes the actual package in global
  • Reinstall it as a local package:
    npm install express

    While the package is in our local application directory (~/projects/test_package/node_modules), it is not installed globally.

  • To link it globally, we can go to the package directory and call the link subcommand without any arguments.
    cd ~/projects/test_package/node_modules/express
    npm link

    Now that it has the proper directory structure and files, we could use the same procedure to make our test package available to other packages we create. Some packages will have shared dependencies. For example, if our package directory has two modules that each need a package called A, that package will be installed twice - once under package1/nodemodules/A, and once under package2/nodemodules/A.

  • We can use the dedupe subcommand to look for these cases and move the shared dependencies up a level. This allows both packages to find the single installation of the dependency.
  • Dedupe the dependencies of our packages in the express directory:
    cd ~/projects/test_package/node_modules/express
    npm dedupe

    This will locate two packages (mine and debug). The debug module is a dependency of another express module called "send". This would typically be deduplicated but since there is a version conflict, nothing is done.

    For example, if you have moved your dependencies upwards by using dedupe, but you then uninstall the packages that previously owned the dependency package, the dependency is not removed due to the fact that it is not within the packages subdirectory anymore.

    To work around this, you can tell npm to "prune" packages that aren't needed in your system. This refers to packages that aren't listed in you parent package's dependency list.

  • Remove unwanted dependencies:
    npm prune

Finding and updating outdated packages

  • Find outdated packages:
    npm outdated
    . . .
    Package  Current  Wanted  Latest   Location
    type-is  1.1.0    1.1.0   1.2.0    express > type-is
    debug    0.8.0    0.8.0 0.8.1      express > send > debug

    This will list packages that have a more recent version available. It will display the installed applications, what your application requested and how that differs from your current version.

  • To update your packages, you need to edit the version requested in the package's "package.json" followed by the update command:
    npm update

Next step

More info


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