I was about to publish a module to NPM, when I thought about rewriting it in ES6, to both future-proof it, and learn ES6. I\'ve used Babel to transpile to ES5, and run tests
The main key in package.json decides the entry point to the package once it's published. So you can put your Babel's output wherever you want and just have to mention the right path in main key.
"main": "./lib/index.js",
Here's a well written article on how to publish an npm package
https://codeburst.io/publish-your-own-npm-package-ff918698d450
Here's a sample repo you can use for reference
https://github.com/flexdinesh/npm-module-boilerplate