JSFiddle - React, Tailwind, and code Playground
HTML
<div id="output"></div>
JavaScript
$("#output").html(
"undefined : " + (undefined ? "true" : "false") + "<br>"
+ "empty : " + ("" ? "true" : "false") + "<br>"
+ "!!empty : " + (!!"" ? "true" : "false") + "<br>"
+ "!!undefined : " + (!!undefined ? "true" : "false"));