InstallNodePackage

We use the npm install command to install new Node packages locally. 
The install command creates a folder called node_modules and copies the package files to it. 
The install command also installs all of the dependencies for the given package.

To install Babel, we need to npm install two packages, babel-cli and babel-preset-env. However,
npm installs over one hundred other packages that are dependencies for Babel to run properly.

We install Babel with the following two commands:

$ npm install babel-cli -D
$ npm install babel-preset-env -D
The babel-cli package includes command line Babel tools, and the babel-preset-env package
has the code that maps any JavaScript feature, ES6 and above (ES6+), to ES5.

The -D flag instructs npm to add each package to a property called devDependencies in package.json.
Once the project’s dependencies are listed in devDependencies, other developers can run your project 
without installing each package separately. Instead, they can simply 
run npm install — it instructs npm to look inside package.json and download all of the packages listed in devDependencies.

Once you npm install packages, you can find the Babel packages and all their dependencies in the node_modules folder. 
The new directory structure contains the following:

project
|_ node_modules
|___ .bin
|___ ...
|_ src
|___ main.js
|_ package.json
The ... in the file structure above is a placeholder for 100+ packages that npm installed.