macht HTTP-Anfragen in Nodejs Schleife

Question

Finden Sie es fast unmöglich, die Antwort von HTTP-Anfragen in einer Schleife als ein Array zu erfassen. Ich kann das Array in console.log sehen, aber wenn ich das Array übergeben, um die Antwort von HTTP-Server zu sein, bekomme ich ein leeres Array. Was mache ich falsch oder gibt es bessere Möglichkeiten?

Code:

router.route('/uprns').post(function(request, response){ 
    response.setHeader('content-type', 'application/text'); 

    console.log('first element from the array is '+request.body.UPRNS[0]); 
    console.log('Number of items in array is '+request.body.UPRNS.length); 

if (request.body.UPRNS.length == 0) { 
     response.send('no UPRNS in request'); 
    } 

    var output = []; 
    var obj = ''; 

    for(var i = 0; i < request.body.UPRNS.length; i++) { 

    obj = request.body.UPRNS[i]; 

    //Make HTTP calls to  
    var options = { 
     host: 'orbisdigital.azure-api.net', 
     path: '/nosecurity/addresses?uprn='+obj // full URL as path 
    }; 

    callback = function(res) {  
     res.on('data', function (chunk) { 
     output.push(chunk.toString()); 
     }); 

     //the whole response has been recieved 
     res.on('end', function() { 
     console.log(output); 
     }); 
    } 

    Https.request(options, callback).end(); 
    } 

    response.send(output); 

}); 

Ich weiß, dass es eine Menge Gerede über Verfahren zur Schleife in einer Blockierung, aber es gibt keinen definitiven empfohlene Weg mit http Anrufen in einer Schleife zu beschäftigen. Danke.

Answer 1

Hier ist der Code. Siehe den Code für die hinzugefügten Kommentare. Lesen Sie etwas über die asynchrone Programmierung mit node.js, here's a starter.

router.route('/uprns').post(function (request, response) { 
    response.setHeader('content-type', 'application/text'); 
    console.log('first element from the array is ' + request.body.UPRNS[ 0 ]); // your 1st element in JSON array. 

    console.log('Number of items in array is ' + request.body.UPRNS.length); 
    var output = []; 
    var obj = ''; 

    for (var i = 0; i < request.body.UPRNS.length; i++) { 

     obj = request.body.UPRNS[ i ]; 

     console.log(obj); 

     //Make HTTP calls to 

     var options = { 
      host: 'orbisdigital.azure-api.net', 
      path: '/nosecurity/addresses?uprn=' + obj // full URL as path 
     }; 

     Https.request(options, callback).end(); 

    } 

    var countResponses = 0; 
    // Don't make functions in a loop, so I moved this function down 
    // here. 
    function callback(res) { 

     res.on('data', function (chunk) { 
      output.push(chunk.toString()); 
     }); 

     // Handles an error 
     request.on('error', function(err) { 
      console.error(err.stack); 
      response.statusCode = 500; // or what ever. 
      response.send(500, 'there was an error'); 
     }); 

     //the whole response has been recieved 
     res.on('end', function() { 
      console.log(output); 
      countResponses++; 
      if (countResponses === request.body.UPRNS.length) { 

       // Previously this code was executed directly 
       // after the loop finished. It did not wait for 
       // all the responses, so it sent the empty response. 
       // However, the other console.log(output) statements 
       // were called after this. 
       // 
       // There is a bug here that if request.body.UPRNS.length 
       // is zero, then the user will never get a response. I 
       // let you fix this up :). 
       response.send(output); 
      } 
     }); 

    } 

}); 

Answer 2

besserer Weg, um solches Szenario zu behandeln ist async.js statt für Schleifen zu verwenden. https://github.com/caolan/async