Waiting till call back completes Node.js

[Pradeep Simha]

My situation is like this, I have a server like this and inside I am calling another callback function which gets multiple values:

    

    var http = require('http'); 

    var server = http.createServer(req,resp) {

         var finalVal = "";

         

         consumer.on('message',function(message) {

             finalVal = message;

             console.log(finalVal);

         });

         resp.end(finalVal);

    });

My finalVal should display all the multiple values it fetches and send it as a response, but problem is it's sending only first value where as console.log displays all the values. I do understand that by the time consumer.on ends response would have committed. Can someone please help me how to handle this scenario since I'm very new to Node.js ? Currently due to heavy deadlines I don't have time to read full information about callbacks. But defnitely I would take time to learn about callbacks.

Here `consumer.on` calls multiple times till it fetches all the data from backend, I need to send all those data in a final response. I am using `node-kafka` to consume to kafka messages.

[greelgorke]

    var http = require('http'); 

    var server = http.createServer(req,resp) {

         var finalVal = "";

         

         consumer.on('message',function(message) {

             finalVal = message;

             console.log(finalVal);
             if(isRealyTheFinalMessage())
                  resp.end(finalVal);

         });

      

    });

[// ravi]

On Aug 12, 2014, at 10:55 PM, Pradeep Simha <pradeep...@gmail.com> wrote:

My situation is like this, I have a server like this and inside I am calling another callback function which gets multiple values:

    

    var http = require('http'); 

    var server = http.createServer(req,resp) {

         var finalVal = "";

         

         consumer.on('message',function(message) {

             finalVal = message;

             console.log(finalVal);

         });

         resp.end(finalVal);

    });

Well, you can move the resp.end() inside the function(message) { } block. But if consumer.on() can fire multiple times and you need to accumulate the messages, how do you know when the data is complete? You will need to add a check for that.

—ravi