I've just started using Grunt.js. It is pretty hard to set up and I am at the point of creating a package.json
file.
Following this tutorial, it says there are 3 ways to create a package.json
file.
The first is to do npm install grunt --save-dev
But what does --save-dev
means? I tried looking but it ends in vain.
--save-dev: Package will appear in your devDependencies.
According to the npm install docs.
If someone is planning on downloading and using your module in their program, then they probably don't want or need to download and build the external test or documentation framework that you use.
In other words, when you run npm install
, your project's devDependencies will be installed, but the devDependencies for any packages that your app depends on will not be installed; further, other apps having your app as a dependency need not install your devDependencies. Such modules should only be needed when developing the app (eg grunt, mocha etc).
According to the package.json docs
Edit: Attempt at visualising what npm install does:
yourproject dependency installed dependency installed dependency installed devDependency NOT installed devDependency NOT installed devDependency installed dependency installed devDependency NOT installed
dependency installed dependency installed dependency installed devDependency NOT installed devDependency NOT installed
dependency installed dependency installed devDependency NOT installed
dependency installed
devDependency NOT installed
devDependency NOT installed
devDependency installed dependency installed devDependency NOT installed
dependency installed
devDependency NOT installed
There are (at least) two types of package dependencies you can indicate in your package.json files:
Those packages that are required in order to use your module are listed under the "dependencies" property. Using npm you can add those dependencies to your package.json file this way: npm install --save packageName Those packages required in order to help develop your module are listed under the "devDependencies" property. These packages are not necessary for others to use the module, but if they want to help develop the module, these packages will be needed. Using npm you can add those devDependencies to your package.json file this way: npm install --save-dev packageName
To add on to Andreas' answer, you can install only the dependencies by using:
npm install --production
When you use the parameter "--save" your dependency will go inside the #1 below in package.json. When you use the parameter "--save-dev" your dependency will go inside the #2 below in package.json.
#1. "dependencies": these packages are required by your application in production.
#2. "devDependencies": these packages are only needed for development and testing
Documentation from npm for npm install <package-name> --save
and npm install <package-name> --save-dev
can be found here:
https://docs.npmjs.com/getting-started/using-a-package.json#the-save-and-save-dev-install-flags
A package.json
file declares metadata about the module you are developing. Both aforementioned commands modify this package.json
file. --save
will declare the installed package (in this case, grunt
) as a dependency for your module; --save-dev
will declare it as a dependency for development of your module.
Ask yourself: will the installed package be required for use of my module, or will it only be required for developing it?
For me the first answer appears a bit confusing, so to make it short and clean:
npm install <package_name>
saves any specified packages into dependencies by default. Additionally, you can control where and how they get saved with some additional flags:
npm install <package_name> --no-save
Prevents saving to dependencies.
npm install <package_name> ---save-dev
updates the devDependencies
in your package. These are only used for local testing and development.
You can read more at in the dcu
Use only when developing
--save-dev means omit in production environments, use only in development environments (smaller, and probably faster).
–save
The package installed is core dependency.
–save-dev
The package installed is not a core rather development dependency.
Success story sharing
npm install --dev
flag?npm install
, the project's devDependencies will also be installed. You don't want a dependency's devDependencies installed. If you want to develop on an npm package, you'dgit clone xxx
that project, and runnpm install
in it.npm install
is run in your project, all devDependencies in package.json will be installed, but if you package your project as a new npm package and publish it, when somebody else installs your package with npm install, the devDependencies will not be installed on their system. Is that right? @stanzheng or you can run npm install --production to install everything in package.json except the dev dependencies