Ajax技术的切换为输入框

1.javascript代码:
<script type="text/javascript">
var req;
var gID;
function changeToInput(id) {
var oNP = document.getElementById(id);
var value = oNP.value;
oNP.outerHTML = "<input type='text' id='" + id + "' value='" + value + "' size='5' onblur='change(this.id)'>";
document.getElementById(id).focus();
}

function change(id) {
var oNP = document.getElementById(id);
var value = oNP.value;
gID = id;
init();
var url = "ChangePrice.jsp?id=" + escape(id) + "&normalprice=" + value;
req.open("GET", url, true);
req.onreadystatechange = callback;
req.send(null);

}

function init() {
if(window.XMLHttpRequest) {
req = new XMLHttpRequest();
} else if (window.ActiveXObject) {
req = new ActiveXObject("Microsoft.XMLHTTP");
}
}

function callback() {
if(4 == req.readyState) {

if(200 == req.status) {

var oNP = document.getElementById(gID);
var value = oNP.value;
oNP.outerHTML = "<span style='background:gray' id='" + gID + "' value='" + value + "' onclick='changeToInput(this.id)'>" + value + "</span>";
}
}

}

</script>

2.<span id="<%=p.getId()%>" style="background:red" onClick="changeToInput(this.id)" value="<%=p.getNormalPrice() %>">
<%=p.getNormalPrice() %>
</span>