使用ajax验证帐号是否重复，使用innerHTML在页面得不到信息

Question

js代码：
var xhr = getXhr();
function getXhr(){
var xhr = null;
try {
xhr = new XMLHttpRequest();
} catch (trymicrosoft) {
try {
xhr = new ActiveXObject("Msxml2.XMLHTTP");
} catch (othermicrosoft) {
try {
xhr = new ActiveXObject("Microsoft.XMLHTTP");
} catch (failed) {
xhr = false;
}
}
}
if (!xhr) {
alert("err Happend!");
}
return xhr;
}
function check() {
var user = document.getElementById("user").value;
var url = "RegisterServlet?id=" + user;
if (xhr.readyState == 4 && xhr.status == 200) {
var str = xhr.responseText;
if (str=="OK") {
document.getElementById("checkname").innerHTML="用户名可用";
} else {
doucument.getElementById("checkname").innerHTML="用户名重复";
}
}
xhr.open('get',url,true);
xhr.send(null);
}
前端代码:

servlet代码:
public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {

    response.setContentType("text/html");
    request.setCharacterEncoding("UTF-8");
    response.setCharacterEncoding("utf-8");
    PrintWriter out=response.getWriter();
    String username=request.getParameter("id");
    System.out.println(username);
    if(username.equals("1")){
        out.println("OK");
    }else {
        out.println("NO");
    }
}
我测试用户名输入是否为1来判断，从servlet传值过来，但是在jsp里面span标签那显示不出来信息,
测试显示这个错误：

ReferenceError: doucument is not defined，报错行数在js的if判断innerhtml行
各位大大帮忙看看

Answer 1

doucument.getElementById("checkname").innerHTML = "用户名重复";

是document，不是doucument，第3,4个字符反了，马虎了