实时获取input框内容

源码：
<%@ page language="java" contentType="text/html; charset=utf-8"
    pageEncoding="utf-8"%>
<!DOCTYPE html>
<html>
<head>
    <script type="text/javascript">
    // Firefox, Google Chrome, Opera, Safari, Internet Explorer from version 9
        function OnInput (event) {
            alert ( event.target.value);
        }
    // Internet Explorer
        function OnPropChanged (event) {
            if (event.propertyName.toLowerCase () == "value") {
                alert ( "123"+event.srcElement.value);
            }
        }
    </script>
</head>
<body>
  <textarea  id="describeInput" placeholder=" 请输入故障描述"  oninput="OnInput (event)" onpropertychange="OnPropChanged (event)" ></textarea>
   
</body>
</html>