Parse change user password

我是Parse的新手，我正在为我的webapp使用Parse Js JDK。我想修改用户的密码。场景是这样的:用户输入旧密码，新密码&确认密码。在提交的形式，我想验证旧密码，如果正确继续设置新密码。通过使用masterKey，我尝试重置用户密码。代码如下:

Parse.Cloud.define("changePassword", function(request, response)
{
  Parse.Cloud.useMasterKey();
  var userId = request.params.userId;
  var newPassword = request.params.password;
  var oldPassword = request.params.oldPassword;
  getUser(userId,oldPassword,newPassword,response);
});
function handleError(error,response)
{
  response.error(error);
}
function handleSuccess(notification,response)
{
    var result = {notification:notification};
    response.success(result);
}
function getUser(userId,oldPassword,newPassword,response)
{
  var User = Parse.Object.extend("User");
  var query = new Parse.Query(User);
  query.get(userId, 
  {
    success: function(user) 
    {
        checkOldPassword(user,oldPassword,newPassword,response); 
    },
    error: function(user, error) 
    {
      handleError(error,response);
    }
  });
}
function checkOldPassword(user,oldPassword,newPassword,response)
{
    var username = user.get("username");
    Parse.User.logIn(username, oldPassword,
    {
        success: function(logedIn)
        {
            changePassword(user,newPassword,response);
        },
        error:function(logedIn,error)
        {
            handleError(error,response);
        }
    });
}
function changePassword(user,newPassword,response)
{
    Parse.User.logOut();
    user.set("password",newPassword);
    user.save(null,
    {
        success: function(userObj)
        {
            handleSuccess("User logged out",response);
        },
        error: function(userObj, error) 
        {
            handleError(error,response);
        }
    });
}