Answer by user16590017 for How to auto-size a textarea in height?

var textarea = document.getElementById("YourTextArea");var limit = 50; //height limittextarea.oninput = function() {  textarea.style.height = "";  textarea.style.height = Math.min(textarea.scrollHeight, limit) +"px";};

textarea {    width: 99%;}

<textarea id="YourTextArea"></textarea>