Javascript 通过Ajax读取JSON没有成功

我有一个节点JS服务器，在这里我使用以下代码从MySQL数据库发送JSON数据：

app.get('/whatever/api/:IDmut', function(req, res) {
  var aquery = 'select * from mutations where id="' + req.param("IDmut") + '"';
  console.log(aquery);
  pool.query(aquery, function select(error, results) {
    res.send(JSON.stringify(results[0]));
  });
});

此JSON如下所示：

{"id":"SL2.50ch02_51010759_11","chr":"SL2.50ch02","pos":51010759,"ref":"T","ale":"A","g001":"0/0:39:99","g002":"0/0:34:99","g003":"0/0:33:99","g004":"0/0:37:99","g005":"0/0:33:99","g006":"0/0:35:99","g007":"0/0:27:99","g008":"0/0:33:99","g011":"0/0:35:99","g012":"0/0:22:85","g013":"0/0:34:99","g014":"0/0:32:99","g015":"0/0:39:99","g016":"0/0:31:99","g017":"0/0:47:99","g018":"0/0:36:99","g019":"0/0:26:97","g020":"0/0:33:99","g021":"0/0:25:94","g022":"0/0:28:99","g023":"0/0:35:99","g024":"0/0:38:99","g025":"0/0:13:58","g026":"0/0:35:99","g027":"0/0:41:99","g028":"0/0:34:99","g029":"0/0:37:99","g030":"0/0:24:91","g031":"0/0:46:99","g032":"0/0:42:99","g033":"0/0:35:99","g034":"0/0:34:99","g035":"0/0:42:99","g036":"0/0:41:99","g037":"0/0:21:82","g038":"0/0:34:99","g039":"0/0:36:99","g040":"0/0:31:99","g041":"0/0:31:99","g042":"0/0:34:99","g043":"0/0:34:99","g044":"0/0:42:99","g045":"0/0:34:99","g046":"0/0:24:91","g047":"0/0:40:99","g049":"0/0:32:99","g051":"0/0:20:79","g052":"0/0:34:99","g053":"0/0:40:99","g054":"0/0:51:99","g055":"0/0:41:99","g056":"0/0:33:99","g057":"0/0:28:99","g058":"0/0:21:82","g059":"0/0:37:99","g060":"0/0:29:99","g063":"0/0:36:99","g064":"0/0:25:94","g065":"0/0:26:97","g066":"0/0:17:70","g067":"0/0:27:99","g068":"0/0:35:99","g069":"0/0:36:99","g070":"0/0:28:99","g071":"0/0:30:99","g072":"0/0:14:61","g073":"0/1:17:99","g074":"0/0:17:70","g077":"0/0:29:99","g078":"0/0:42:99","g088":"0/0:18:73","g089":"0/0:26:97","g090":"0/0:40:99","g091":"0/0:29:99","g093":"0/0:37:99","g094":"0/0:26:97","g096":"0/0:28:99","g097":"0/0:41:99","g102":"0/0:33:99","g103":"0/0:19:76","g104":"0/0:19:76","g105":"0/0:27:99"}

在clident方面，我有以下代码：

$.ajax({
    type:     "GET",
    url:      "the corresponding url... it is provate so...",
    dataType: "json",
    success: function(data){alert(data);}
});

这是行不通的。任何地方都没有警报。但是，如果我将url更改为

http://echo.jsontest.com/key/value/anotherKey/anotherValue

，这很有效

编辑：我刚刚在控制台上看到这个错误：

加载资源失败：服务器响应状态为401（未授权）

---

请求的资源上不存在“Access Control Allow Origin”头。因此，不允许访问源“externalfile://”。响应的HTTP状态代码为401。

也许您应该改用res.json？

试试这个（注意：唯一的区别是数据类型不是“json”，而是“jsonp”）

---

根据您得到的错误，这听起来像是CORS问题（）。您正试图向其他服务器发出HTTP请求，但服务器拒绝了该请求，因为您没有正确的访问控制标头设置

是一个很好的Node和Express库，它提供了添加头的中间件

本质上，它归结为拥有

Access-Control-Allow-Origin : *

---

标题在您的答复上。此标头将允许其他域向您的web服务器发出请求。您可以设置允许发出请求的特定白名单URL，或只设置一个*以允许任何域向您的服务器发出请求。

在服务器端？不，我的意思是在客户端，使用浏览器中的开发工具检查实际请求，至少提供一些疑难解答信息。我更新了答案…添加到$.ajax（）中，错误：function（err）{alert（err）；}一个问题怎么可能是答案？这只不过是一个评论而已

Access-Control-Allow-Origin : *