textarea 늘어나게 하는 방법

https://zetawiki.com/wiki/HTML_textarea_%EC%9E%90%EB%8F%99_%EB%86%92%EC%9D%B4_%EC%A1%B0%EC%A0%88

<style>
textarea.autosize { min-height: 50px; }
</style>

<textarea class="autosize" onkeydown="resize(this)" onkeyup="resize(this)" placeholder="추가 바람"></textarea>

<script>
function resize(obj) {
  obj.style.height = "1px";
  obj.style.height = (12+obj.scrollHeight)+"px";
}
</script>