npm Install

I've been using npm without giving much thought... Here's a quick post on a couple of options that I wanted to know more about.

npm install [package name] -g (or --global)

• Installs a package in global mode, and not under your local project/package. For Windows, %APPDATA%\npm (e.g., C:\Users\[Username]\AppData\Roaming\npm). Note that this is not where Node.js and npm is installed, that's usually C:\Program Files\nodejs.
• It's mainly for packages with executables, as they will become available from everywhere, since above directory is added to the PATH when you install Node.js (when installed with default options).
• It does not modify package.json of your current project.

An example – let's install Angular CLI:

• npm install @angular/cli -g

After running the command, in the directory mentioned above:

• ng (for bash) and ng.cmd (for Windows) will be added, so you can run ng from any command line window.
• node_modules\@angular will be added.

npm install [package name] --save-dev (or -D)

The package will appear under devDependencies. This means that when you run npm install in production mode, the package will not be installed.

devDependencies are things you need during development and not necessarily in production, such as a unit testing framework.

You might come across npm --save. This has been deprecated, since it's the default option now – npm will add the package under the dependencies section in addition to installing it under node_modules.

How do you run npm install in production mode?

• npm install --production
• If NODE_ENV is set to production, then simply npm install
• To force, regardless of NODE_ENV variable, then npm --only=prod

You can't have a package in both devDependencies and dependencies.

Production mode is more important for server-side apps, i.e., using Node.js. For front-end, if you're just publishing the files after running through a package manager such as WebPack, probably should still be okay to use them as intended, though may need further investigation...

Some other tidbits

• If you run npm install, npm will traverse up to find the root of your project, i.e., the directory with package.json, and install under node_modules from the directory accordingly. If package.json is not found, it will just use the current directory as root.
• In npm lingo, prefix is the root directory of your project, or the global npm directory if -g is used.

Screenshot of Node.js installation step where you specify that npm global directory should be added to the path.

See also: npm docs - npm-folders, npm-install.