What cause "Error: Uncaught (in promise): Response with status:200 for Url:null" to show up?

Question

我正在通过 NodeJS 和 Express 访问 Mongo 数据库，如下所示：

var MongoClient = require('mongodb').MongoClient;
    ...
    app.get("/app/visits", function (req, res, next) {
      console.log("get visits");
      MongoClient.connect('mongodb://localhost:27017/db', function (err, db) {
        if (!err) { console.log("We are connected"); }
        visits = db.collection('visits', function (err, collection) { });
        visits.find().toArray(function (err, user) {
          this.user = JSON.stringify(user);
          if (err) { throw err; } else console.dir(this.user);
        });
        res.send(this.user);
      });
    });

在浏览器中这工作正常。如果我将 res.send(this.user); 更改为 res.status(301).send(this.user);，状态也会更改。但是问题是，Angular 2 用原生脚本代码 returns 报错：

getActualVisits()
     {  
        return this.http.get("http://localhost:1234/app/visits").map(response => response.json())
      }

在尝试修复 7 小时后，我不知道为什么。方法 getActualVisits() 调用自：

 getActualSpecialization() {
    let v = this.getActualVisits();
...
}

Answer 1

您需要在 .map 之后调用 .subscribe 以观察返回的值。

getActualVisits() {  
    return this.http.get("http://localhost:1234/app/visits")
        .map(response => response.json())
        .subscribe(
            data => this.actualVisits = data,
            err => this.logError(err),
            () => console.log('get actual visits complete')
         );
}

有关详细信息，请参阅以下文档https://auth0.com/blog/2015/10/15/angular-2-series-part-3-using-http/

What cause "Error: Uncaught (in promise): Response with status:200 for Url:null" to show up?

What cause "Error: Uncaught (in promise): Response with status:200 for Url:null" to show up?

javascript

node.js

nativescript

angular