JSFiddle - React, Tailwind, and code Playground

by Nir Azuelos

HTML

<textarea rows="1" style="height:1em;" id="text"></textarea>

CSS

textarea {
 border: 0 none white;
 overflow: hidden;
 padding: 0;
 outline: none;
 background-color: #D0D0D0;
 resize: none;
}

JavaScript

var observe;
if (window.attachEvent) {
 observe = function (element, event, handler) {
  element.attachEvent('on'+event, handler);
 };
}
else {
 observe = function (element, event, handler) {
  element.addEventListener(event, handler, false);
 };
}
function init () {
 var text = document.getElementById('text');
 function resize () {
   var scrollLeft = window.pageXOffset ||
   (document.documentElement || document.body.parentNode || document.body).scrollLeft;

   var scrollTop  = window.pageYOffset ||
   (document.documentElement || document.body.parentNode || document.body).scrollTop;

   text.style.height = "auto";
   text.style.height = text.scrollHeight + 'px';

   window.scrollTo(scrollLeft, scrollTop);
 }
 /* 0-timeout to get the already changed text */
 function delayedResize () {
  window.setTimeout(resize, 0);
 }
 observe(text, 'change',  resize);
 observe(text, 'cut',     delayedResize);
 observe(text, 'paste',   delayedResize);
 observe(text, 'drop',    delayedResize);
 observe(text, 'keydown', delayedResize);

 text.focus();
 text.select();
 resize();
}

init();