输入内容时，textarea 将自动增长

<style>

textarea.noscrollbars {

  overflow: hidden;

  width: 300px;

  height: 100px;

}

</style>

​

<script>

function autoGrow (oField) {

  if (oField.scrollHeight > oField.clientHeight) {

    oField.style.height = oField.scrollHeight + "px";

  }

}

</script>

​

<form>

  <fieldset>

    <legend>您的评论</legend>

    <p><textarea class="noscrollbars" onkeyup="autoGrow(this);"></textarea></p>

    <p><input type="submit" value="发送" /></p>

  </fieldset>

</form>

​