在mui.ajax 的success回调函数里调用5+ api提示plus is not defined

贴一下代码，贴一下报错误的console截图

mui.plusReady(function(){  
        document.getElementById('login').addEventListener('tap',function(e){  
        var username = document.getElementById('username');  
        var pwd = document.getElementById('userPwd');  
        mui.ajax('http://goochange.kdapp.net/communication/interface',  
            {data:{  
                actiontype:'rfjSE2Gujo8SMUQnTDqfspwTuczHl68J',  
                username:username.value,  
                pwd:pwd.value  
                },  
            dataType:'json',  
            type:'post',  
            timeout:5000,  
            success:function(data){  
                if(data.length>0){  
                       UserInfo.clear(); //清除登录状态信息  
                    UserInfo.username(data[0].userName);  
                    UserInfo.password(data[0].userRealName);  
                    UserInfo.token(data[0].userId);  

                    mui.toast('登入成功！');  
                    mui.fire(plus.webview.getWebviewById('index-menu'),'login',{status:'注銷登入'});  
                    mui.fire(plus.webview.getLaunchWebview(),'showAllWebview',{});  
                    plus.webview.currentWebview().close();  
                }else{  
                    mui.toast('用戶名或密碼錯誤，請重新輸入 !');  
                    }  
                    }  
        })  
    })  
})