JS监听输入框值变化兼容 onpropertychange、oninput

<script type="text/javascript">
function immediately() {
element = document.getElementById("mytext");
if (window.ActiveXObject) {
element.onpropertychange = webChange;
} else {
element.addEventListener("input", webChange, false);
}
}
function webChange() {
if (element.value) {
document.getElementById("test").innerHTML = element.value;
}
;
}
</script>

Input：
<input type="text" name="textfield" oninput="document.getElementById('webtest').innerHTML=this.value;" onpropertychange="document.getElementById('webtest').innerHTML=this.value;" />
<div>您输入的值为：<span id="webtest"></span></div>
<br /><br /><br /><br /><br />
JS：
<input type="text" name="textfield" id="mytext" />
<div>您输入的值为：<span id="test"></span></div>
<script type="text/javascript">
immediately();
</script>