var xhr = new XMLHttpRequest();
xhr.onreadystatechange = function(){
    if (this.readyState == 4 && this.status == 200){
        //创建隐藏的下载链接
        console.log(this.response, typeof this.response);
        var downloadLink = document.createElement('a');
        downloadLink.style.display = 'none';
        downloadLink.download = "测试.xls";
        var URL = window.URL || window.webkitURL;
        downloadLink.href = URL.createObjectURL(this.response);
        document.body.appendChild(downloadLink);
        //触发click
        var event = document.createEvent("MouseEvents");
        event.initMouseEvent(
            "click", true, false, window, 0, 0, 0, 0, 0
            , false, false, false, false, 0, null
        );
        downloadLink.dispatchEvent(event);
        //URL.revokeObjectURL(iframe.src);
    }
}
xhr.open('POST', url);
xhr.setRequestHeader('Content-Type', 'application/x-www-form-urlencoded; charset=UTF-8');
xhr.responseType = 'blob';
xhr.send($.param({name:'test'}));