使用來自http.get的數據更新app.get響應

Question

我正在使用express和傳遞路徑作為url參數。

app.get("/download", function (req, res) {
    var location;
    var options = {
        host: 'example.com',
        port: 80,
        path: req.query.url.replace(/ /g, "%20")
    };

    http.get(options, function (res) {

        // get location from this 

        location = res.headers.location;
        console.log(location);

    }).on('error', function (e) {
        console.log("Got error: " + e.message);
    });

    // it won't get the location data since http.get is async
    // so how could I send this response using the data from http.get

    res.setHeader('Content-Type', 'text/html');
    res.send(location);
});

在這段代碼中，我希望從http.get的請求頭中檢索數據，以便在瀏覽器上進行渲染。

無論如何，我可以做到在瀏覽器上呈現http.get數據。

Answer 1

你不能只在函數內移動res.send() ，例如：

app.get("/download", function (req, res) {
    var location;
    var options = {
        host: 'example.com',
        port: 80,
        path: req.query.url.replace(/ /g, "%20")
    };

    http.get(options, function (response) {

        // get location from this 

        location = response.headers.location;
        console.log(location);

        res.setHeader('Content-Type', 'text/html');
        res.send(location);

    }).on('error', function (e) {
        console.log("Got error: " + e.message);
        res.send('Error...')
    });

});

我還建議使用請求包來發出HTTP請求，因為它可以使整個過程更簡單。

Answer 2

您可以通過使用中間件將數據從“GET”查詢傳遞到example.com 。 中間件將攔截對應用程序的任何請求，執行其中定義的任何操作，並將控制權傳遞回該請求的處理程序。

// Define middleware that makes a 'GET' request to 'example.com' and obtains the location.
app.use(function(req, res, next) {
  var options = {
      host: 'example.com',
      port: 80,
      path: req.query.url.replace(/ /g, "%20")
  };

  http.get(options, function (res) {

      // Attach the location to the request object. This will be present
      // in the request object of the 'GET' handler for the app.
      req.webLocation = res.headers.location;

      // Execute the next middleware or the route handler if there's no
      // other middleware.
      next();

  }).on('error', function (e) {
      console.log("Got error: " + e.message);
  });
});

app.get("/", function (req, res) {

    res.setHeader('Content-Type', 'text/html');
    // Render the 'webLocation' obtained from the middleware.
    res.send(req.webLocation);
});