Npm 安装的 -- save 选项是什么？

I saw some tutorial where the command was:

npm install --save

What does the --save option mean?

Not able to find the answer on Google.

Update npm 5:

As of npm 5.0.0, installed modules are added as a dependency by default, so the --save option is no longer needed. The other save options still exist and are listed in the documentation for npm install.

Original answer:

Before version 5, NPM simply installed a package under node_modules by default. When you were trying to install dependencies for your app/module, you would need to first install them, and then add them (along with the appropriate version number) to the dependencies section of your package.json.

The --save option instructed NPM to include the package inside of the dependencies section of your package.json automatically, thus saving you an additional step.

In addition, there are the complementary options --save-dev and --save-optional which save the package under devDependencies and optionalDependencies, respectively. This is useful when installing development-only packages, like grunt or your testing library.

It won't do anything if you don't have a package.json file. Start by running npm init to create one. Then calls to npm install --save or npm install --save-dev or npm install --save-optional will update the package.json to list your dependencies.

To add package in dependencies:

npm install my_dep --save

or

npm install my_dep -S

To add package in devDependencies

npm install my_test_framework --save-dev

or

npm install my_test_framework -D

package.json

You can also use -S, -D or -P which are equivalent of saving the package to an app dependency, a dev dependency or prod dependency. See more NPM shortcuts below:

-v: --version
-h, -?, --help, -H: --usage
-s, --silent: --loglevel silent
-q, --quiet: --loglevel warn
-d: --loglevel info
-dd, --verbose: --loglevel verbose
-ddd: --loglevel silly
-g: --global
-C: --prefix
-l: --long
-m: --message
-p, --porcelain: --parseable
-reg: --registry
-f: --force
-desc: --description
-S: --save
-P: --save-prod
-D: --save-dev
-O: --save-optional
-B: --save-bundle
-E: --save-exact
-y: --yes
-n: --yes false
ll and la commands: ls --long

npm install package_x --save

The given package (package_x) will be saved in package.json inside dependencies. if you add

npm install <> --save-dev

then it will be saved inside "devDependencies".

As of npm 5, it is more favorable to use --save-prod (or -P) than --save but doing the same thing, as is stated in npm install. So far, --save still works if provided.

As of npm 5, npm will now save by default. In case,if you would like npm to work in a similar old fashion (no autosave) to how it was working in previous versions, you can update the config option to enable autosave as below.

npm config set save false

To get the current setting, you can execute the following command:

npm config get save

Source:https://blog.pusher.com/what-you-need-know-npm-5/

npm i (Package name) --save

Simplily, using above command we ll not need to write package name in your package.json file it ll auto add its name and dependency with version that you ll need at time when you go for production or setup another time.

npm help install

Above command ll help find out more option and correct def.shown in pic

according to NPM Doc

So it seems that by running npm install package_name, the package dependency should be automatically added to package.json right?

The easier (and more awesome) way to add dependencies to your package.json is to do so from the command line, flagging the npm install command with either --save or --save-dev, depending on how you'd like to use that dependency.