Formats a Date as yyyy-MM-dd.
$ npm install yyyy-mm-dd (...) $ node > let yyyymmdd = require('yyyy-mm-dd') undefined > yyyymmdd() '2015-04-29' > yyyymmdd.withTime() '2015-04-29 16:51:09' > yyyymmdd(new Date(1999, 0, 1)) '1999-01-01'