JSFiddle - React, Tailwind, and code Playground

HTML

<textarea cols="42" rows="1">
1 ...by default, you can write more rows</textarea><br />
<br />
<textarea cols="42" rows="5">
1
2
3
4
5 ...by default, you can write more rows</textarea><br />
<br />
<textarea cols="42" rows="10">
1
2
3
4
5
6
7
8
9
10 ...by default, you can write more rows</textarea>

CSS

textarea {
  border: 1px solid gray;
  border-radius: 3px;
  line-height: 1.3em;
  overflow: hidden;
  padding: 0.3em 0.3em 0 0.3em;
  outline: none;
  background-color: white;
  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 () {
  function resize (element) {
    element.style.height = 'auto';
    element.style.height = element.scrollHeight+'px';
  }
  /* 0-timeout to get the already changed text */
  function delayedResize (element) {
    window.setTimeout(function() { resize(element) }, 0);
  }
  var textareas = document.getElementsByTagName("textarea");
  for (i = 0; i < textareas.length; i++) {
    var textarea = textareas[i];
    observe(textarea, 'change', function() { resize(this) });
    observe(textarea, 'cut', function() { delayedResize(this) });
    observe(textarea, 'paste', function() { delayedResize(this) });
    observe(textarea, 'drop',function() { delayedResize(this) });
    observe(textarea, 'keydown', function() { delayedResize(this) });
    textarea.focus();
    textarea.select();
    resize(textarea);
  }
}

init();