The thing about npm

I. What is npm

npm is a package management tool officially provided by node, which is used to solve the problem of node code deployment. When installing Node.js, the corresponding npm version will be automatically installed.

Using the npm package management tool can solve the needs of the following scenarios:

• Download third-party packages written by others from the npm server to the local
• Download and install the command program written by others from the npm server to the local
• Upload your own package or command-line program to the npm server for others to use

Second, commonly used npm commands

npm install: To install all the packages required by the project, you need to configure the package.json file
npm uninstall: to uninstall the package of the specified name
npm update: to update the package of the specified name
npm start: to start the project
npm run bulid: project build
npm init: used to initialize and generate a new package.json file
npm set: used to set environment variables
npm info: view the specific information of each module

About the difference between npm install, npm install --save, npm install --save -dev and npm install -g

npm install:
will install the X package into the node_modules directory
will not modify package.json
run npm install, the X package will not be downloaded automatically

npm install --save:
The X package will be installed in the node_modules directory
X will be added under the dependencies property of package.json
Run npm install, it will beAutomatically install the X package into node_modules
After running npm install --production or specify the NODE_ENV variable value as production, X will be automatically installed in the node_modules directory

npm install --save -dev:
will install the X package into the node_modules directory
will add X under the dependencies property of package.json
run npm install, the X package will be automatically installed into node_modules
After running npm install –production or when the NODE_ENV variable value is marked as production, X will not be automatically installed in the node_modules directory

npm install -g:
The X package will be installed directly globally and will not appear in node_modules
The X package will not be automatically downloaded when running npm install

Summary
npm install just downloads the dependencies locally and does not modify package.json.
npm install -save will download the dependencies to the local, and modify the package.json, the project initialization npm install will download.
npm install --save-dev indicates that this dependency is only used in the development environment. If the project is packaged, this dependency will not be added to the build package.Use --save for packages that need to be used at runtime, otherwise use --save -dev.
npm install -g: download locally and globally without modifying package.json.