dom - Ext JS Iframe GET 请求

Question

我想使用警报显示服务器响应

    Ext.getBody().mask('Downloading file....', 'x-mask-loading');
    var iframe = Ext.getBody().createChild({
        tag: 'iframe',
        cls: 'x-hidden',
        src: downldObj.url
    });
    iframe.on('readystatechange', function () {
        if (iframe.dom.readyState === 'loading') {
            return;
        }
        Ext.getBody().unmask();
        iframe.remove.defer(1000, iframe);
    });

如何从我正在执行的服务器代码向用户获取服务器响应警报 Response.status(Status.Error ,"Downloading falied","application/json").header("Content-Type", "text/html" )