JSFiddle - React, Tailwind, and code Playground

HTML

<textarea id="test"></textarea>

CSS

#test { border-color: red; }
#test:focus { border-color: green !important; outline: none; }

JavaScript

document.getElementById("test").addEventListener("keydown", controlBorderColor, false);
document.getElementById("test").addEventListener("keyup", controlBorderColor, false);

function controlBorderColor() {
  if (this.value.length == 0) { this.style.borderColor = "red"; $.now();}
  else { this.style.borderColor = "blue"; }
}