textarea自适应高度

<textarea type="text" rows="3" cols="50" required='required' class="noscrollbars" id="noscrollbars" oninput="autoGrow(this);" placeholder="描述一下任务的要求与限制"></textarea>

JS代码：
function autoGrow (oField) {
oField.style.height = '40px';
oField.style.height = oField.scrollHeight + "px";
}