NPM

Also known as Node Package Manager
Used to install dependencies, share and consume useful and reusable code
Originally used as a package manager for Node.js (which is a javascript framework for writing server-side applications)
NPM is now the 'GOTO' for all front-end javascript frameworks as well, including: React, Vue, Angular, Redux, GraphQL, Fabric UI, Babel, WebPack, Yeoman
There have been a number of attempts to de-throne NPM but NPM is king Twitter created Bower in 2014 and Facebook created Yarn in 2016, both have lost momentum


npm is written using node.js
Before you can use npm you must install node.js first.


Install node.js and npm

visit nodejs.org and download for Windows.
When you download node.js you automatically get npm installed as well.
This installs into the following folder:

C:\program Files\nodejs\ 

You will need to restart your computer.


Check Installation

To check which packages are installed globally
You can use "-g" or "--g".

npm list -g 
npm list --g

Check that node and npm are installed.
Open a command prompt and type following.

node -v 
npm -v

If you do not see version numbers then these are not installed.
node - 10.14.1
npm - 6.4.1
To install newer versions of Node and NPM download the installer from nodejs.org and run it again.
https://www.tutorialspoint.com/reactjs/reactjs_environment_setup.htm


Switches

npm install -g _ is the global install flag 
npm install -save _ means the package will appear in your dependencies
npm install -save-dev _ means the package will appear in your devDependencies
npm install -save-optional _ means the package will appear in your optionalDependencies


dependencies - these are modules required at runtime (--save)
devDependencies - these are modules only required during development (--save-dev)



Latest Versions

npm install  //installs all modules that are listed in the package.json file 
npm update //updates all the packages in the node_modules and their directory dependencies


More

npm install --save-dev babel-preset-react ??? 
npm install --save-dev source-map-loader ???

npm cache clean --force



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