The difference between NPM install -g/-save/-save-dev

npm install XX （ Shorthand for npm i XX）

• Will be able to XX Package installed in node_modules Directory
• stay npm5 Before the release ,XX Will not automatically write package.json
• stay npm5 Then it will be written automatically package.json Of dependencies Properties of the （ And --save identical ）

npm install XX -g

• -g Means to install the module to overall situation , Where to install on the disk , Want to see npm config prefix The location of

• The specific check method is to input npm config edit, Find in the pop-up document ; prefix=C:\node Is it

npm install XX --save( Shorthand for npm i XX -S)

• Will be able to XX Package installed in node_modules Directory ,

• Will be in package.json Of dependencies Add... Under properties XX

• - function npm install --production Or annotate NODE_ENV Variable value is production when （ Installation in production environment depends on ）, The module will be automatically downloaded to node_modules Directory .

• stay npm5 Then it can be npm i xx replace

dependencies The dependency in is Dependencies in the production environment , It will also be installed in the production environment after the project deployment , for example :

It was used axios request , Because it still needs to be used after release to production axios, This will make axios The installation to dependencies

npm install XX --save-dev( Shorthand for npm i XX -D)

• Will be able to XX Package installed in node_modules Directory

• Will be in package.json Of devDependencies Add... Under properties XX

• function npm install --production Or annotate NODE_ENV Variable value is production when （ Installation in production environment depends on ）, Modules will not be automatically downloaded to node_modules Directory .

devDependencies The dependency in is Dependency only in the development environment , It will not be installed in the production environment after the project deployment , for example :

Write ES6 Code , need babel convert to es5 , After the conversion , We just need the converted code , When you go online , Directly deploy the converted code to the production environment , Unwanted bebal 了 , The production environment doesn't need , This will make babel The installation to devDependencies