npm install是否排除dev依赖项？

Question

When I am in a Node.js project and run npm install , npm installs both, dependencies and dev dependencies. If I do not want to install the dev dependencies, I can run npm install --production .

Question 1: If I do not provide --production : Are the dependencies' dev dependencies installed, too, or only their actual dependencies?

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Now, what if I am in a Node.js project and install a new dependency, something such as:

npm install foo

This installs foo 's dependencies, of course.

Question 2: But what about its dev dependencies? Are they installed, too, or are they skipped?

Answer 1

Answers to your questions:

1. Yes dev dependencies will be installed in npm install only way it wont install dev dependencies is when NODE_ENV is set to production
2. No dev dependencies of your external modules won't be installed see here

Answer 2

When you run npm install by default both dependencies and devDependency dependencies are also installed. Because if once is going to develop a package, we would download it eg from git and go to root folder and run.

npm install 

so you would expect to have devDependencies to.

npm install "$package"

doesn't install the devDependencies by default. But if you really want to install development packages in that case, you can set the dev config option to true:

npm install "$package" --dev

Answer 3

Node applications use multiple methods to maintain dependency versioning up to date but there are multiple dependency types that need to be considered. Dependencies are found in a node application's root directory within the package.json file. I will go through the different dependency types and list some defining features or characteristics:

Dependencies: These 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.

npm install from a directory that contains package.json npm install $package on any other directory dependencies are required to run Installed transitively: if A requires B, and B requires C. then C gets installed, otherwise B could not work, and neither would A. devDependencies: If someone is planning on downloading and using 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 this case it's best to map these additional items in a devDependencies object, which is not installed when the user is installing the package unless specifically passing in --dev. These are typically installed when doing a traditional npm install from the root of the package.

npm install on a directory that contains package.json, unless the developer passes the --production flag.
not installed on npm install "$package" on any other directory, unless you give it the --dev option Are not installed transitively Other Dependency types: These are less commonly used but may serve a purpose.

peerDependencies optionalDependencies