jQuery addClass example

Change class name on click in jQuery

HTML

Text area lines: <input id="lineNoInput" type="number" name="lines" value="2">
<br/><br/>
<textarea id="textArea" name="text" form="usrform" rows="2" cols="36">Enter text here...</textarea>

JavaScript

$('#lineNoInput').on("change paste keyup", function() {
    $('#textArea').attr('rows', $('#lineNoInput').val());
});