What is the difference between --save and --save-d

问题:

What is the difference between:

npm install [package_name] --save

and

npm install [package_name] --save-dev

What does this mean?

回答1:

• --save-dev is used to save the package for development purpose. Example: unit tests, minification..
• --save is used to save the package required for the application to run.

回答2:

The difference between --save and --save-dev may not be immediately noticable if you have tried them both on your own projects. So here are a few examples...

Lets say you were bulding an app that that used the moment package to parse and display dates. Your app is a scheduler so it really needs this package to run, as in: cannot run without it. In this case you would use

npm install moment --save

This would create a new value in your package.json

"dependencies": {
   ...
   "moment": "^2.17.1"
}

When you are developing, it really helps to use tools such as test suites and may need jasmine-core and karma. In this case you would use

npm install jasmine-core --save-dev
npm install karma --save-dev

This would also create a new value in your package.json

"devDependencies": {
    ...
    "jasmine-core": "^2.5.2",
    "karma": "^1.4.1",
}

You do not need the test suite to run the app in its normal state, so it is a --save-dev type dependency, nothing more. You can see how if you do not understand what is really happening, it is a bit hard to imagine.

Taken directly from NPM docs docs#dependencies

Dependencies

Dependencies are specified in a simple object that maps a package name to a version range. The version range is a string which has one or more space-separated descriptors. Dependencies can also be identified with a tarball or git URL.

Please do not put test harnesses or transpilers in your dependencies object. See devDependencies, below.

Even in the docs, it asks you to use --save-dev for modules such as test harnesses.

I hope this helps and is clear.

回答3:

By default, NPM simply installs a package under node_modules. When you're trying to install dependencies for your app/module, you would need to first install them, and then add them to the dependencies section of your package.json.

--save-dev adds the third-party package to the package's development dependencies. It won't be installed when someone installs your package. It's typically only installed if someone clones your source repository and runs npm install in it.

--save adds the third-party package to the package's dependencies. It will be installed together with the package whenever someone runs npm install package.

Dev dependencies are those dependencies that are only needed for developing the package. That can include test runners, compilers, packagers, etc. Both types of dependencies are stored in the package's package.json file. --save adds to dependencies, --save-dev adds to devDependencies

npm install documentation can be referred here.

回答4:

A perfect example of this is:

$ npm install typescript --save-dev

In this case, you'd want to have Typescript (a javascript-parseable coding language) available for development, but once the app is deployed, it is no longer necessary, as all of the code has been transpiled to javascript. As such, it would make no sense to include it in the published app. Indeed, it would only take up space and increase download times.

回答5:

As suggested by @andreas-hultgren in this answer and according to the npm 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.

However, for webapp development, Yeoman (a scaffolding tool that installs a peer-reviewed, pre-written package.json file amongst other things) places all packages in devDependencies and nothing in dependencies, so it appears that the use of --save-dev is a safe bet in webapp development, at least.

回答6:

--save-dev saves semver spec into "devDependencies" array in your package descriptor file, --save saves it into "dependencies" instead.

回答7:

--save-dev is used for modules used in development of the application,not require while running it in production envionment --save is used to add it in package.json and it is required for running of the application.

Example: express,body-parser,lodash,helmet,mysql all these are used while running the application use --save to put in dependencies while mocha,istanbul,chai,sonarqube-scanner all are used during development ,so put those in dev-dependencies .

npm link or npm install will also install the dev-dependency modules along with dependency modules in your project folder

回答8:

Clear answers are already provided. But it's worth mentioning how devDependencies affects installing packages:

By default, npm install will install all modules listed as dependencies in package.json . With the --production flag (or when the NODE_ENV environment variable is set to production ), npm will not install modules listed in devDependencies .

See: https://docs.npmjs.com/cli/install

回答9:

You generally don't want to bloat production package with things that you only intend to use for development purposes. So use --save-dev (or -D) option to separate those packages such as watchers(nodemon), unit test frameworks(jest, jasmine, mocha, chai etc.etc.)

Any other library packages that are must for your app to function need to be installed using --save (or -S)

npm install --save lodash       //prod dependency
npm install -S moment           // "       "
npm install -S opentracing      // "       "

npm install -D jest                 //dev only dependency
npm install --save-dev typescript   //dev only dependency

If you open the package.json file then you will see these entries listed under two different sections:

"dependencies": {
  "lodash": "4.x",
  "moment": "2.x",
  "opentracing": "^0.14.1"
},

"devDependencies": {
    "jest": "22.x",
    "typescript": "^2.8.3"
},

回答10:

I want to add some my ideas as

I think all differents will appear when someone use your codes instead of using by yourself

For example, you write a HTTP library called node's request

In your library,

you used lodash to handle string and object, without lodash, your codes cannot run

If someone use your HTTP library as a part of his codes. Your codes will be compiled with his.

your codes need lodash, So you need put in dependencies to compile

---

If you write a project like monaco-editor, which is a web editor,

you have bundle all your codes and your product env library using webpack, when build completed, only have a monaco-min.js

So someone don't case whether --save or --save-dependencies, only he need is monaco-min.js

Summary:

1. If someone want to compile your codes (use as library), put lodash which used by your codes into dependencies

2. If someone want add more feature to your codes, he need unit test and compiler, put these into dev-dependencies