add-demo-npm-hyj-first-try v0.1.0

developing-and-publishing-a-typescript-npm-package

https://codeburst.io/developing-and-publishing-a-typescript-npm-package-d9fc643d4229

how to setup new typescript project

https://www.digitalocean.com/community/tutorials/typescript-new-project

what is nyc?

:It shows the coverage of test https://www.npmjs.com/package/nyc https://dev.to/danywalls/code-coverage-in-2-minutes-with-nyc-130m

configuring esLint guide

https://eslint.org/docs/2.0.0/user-guide/configuring