Resize TextArea

Expand textarea on adding/pasting text and decrease the size on deleting text - plain javascript

by Kurenaikunai

HTML

<textarea onkeyup="onKeyPressTextMessage(event)" name="welcomeContentTmpl" id="welcomeContent" rows="2" cols="40" maxlength="320"></textarea>

JavaScript

onKeyPressTextMessage = function() {
  var textArea = event.currentTarget;
  textArea.style.height = 'auto';
  textArea.style.height = textArea.scrollHeight + 'px';
};