I am trying to retrieve a json object to use it in another module, but I have a problem with callback. I have the error "callback is not a function". I use callback because my variable description is undefined, so i guess it's a problem of asynchronous.

Could you help me plz :)

var leboncoin = function () {
    var http = require('http')
    var bl = require('bl')

    http.get("", function (response, callback) {
        response.pipe(bl(function (err, data) {
            if (err) {
                return console.error(err)
                callback(err);
            }
            var data = data.toString()

            var brand = ...
            var model = ...
            var releaseDate = ...
            var km = ...
            var fuel = ...
            var gearbox = ...

            description.Brand = brand;
            description.Model = model;
            description.Year = releaseDate;
            description.KM = km;
            description.Fuel = fuel;
            description.Gearbox = gearbox;

            callback(description);
            return (description)

            /*console.log(description.Brand);
            console.log(description.Model);
            console.log(description.Year);
            console.log(description.KM);
            console.log(description.Fuel);
            console.log(description.Gearbox);*/

        }))
    })
}

exports.leboncoin = leboncoin;

var module = require('./leboncoin');
var res = module.leboncoin();

console.log(res);

I am trying to retrieve a json object to use it in another module, but I have a problem with callback. I have the error "callback is not a function". I use callback because my variable description is undefined, so i guess it's a problem of asynchronous.

Could you help me plz :)

var leboncoin = function () {
    var http = require('http')
    var bl = require('bl')

    http.get("http://www.website.", function (response, callback) {
        response.pipe(bl(function (err, data) {
            if (err) {
                return console.error(err)
                callback(err);
            }
            var data = data.toString()

            var brand = ...
            var model = ...
            var releaseDate = ...
            var km = ...
            var fuel = ...
            var gearbox = ...

            description.Brand = brand;
            description.Model = model;
            description.Year = releaseDate;
            description.KM = km;
            description.Fuel = fuel;
            description.Gearbox = gearbox;

            callback(description);
            return (description)

            /*console.log(description.Brand);
            console.log(description.Model);
            console.log(description.Year);
            console.log(description.KM);
            console.log(description.Fuel);
            console.log(description.Gearbox);*/

        }))
    })
}

exports.leboncoin = leboncoin;

var module = require('./leboncoin');
var res = module.leboncoin();

console.log(res);

• javascript
• node.js

• where does said error happen within the given code? – Kevin B Commented Oct 14, 2015 at 17:58
• 4 nodejs/api/http.html#http_event_response, it doesn't have the 2nd param – fuyushimoya Commented Oct 14, 2015 at 17:59
• The error is at the line "callback (description)" – Peter Commented Oct 14, 2015 at 18:02
• The callback function is undefined... – Danny Fardy Jhonston Bermúdez Commented Oct 14, 2015 at 18:03

2 Answers 2

Callbacks aren't magic that just appear. You need to define a parameter to your function and pass the callback you want to use.

// --------------------------v
var leboncoin = function (callback) {
    var http = require('http')
    var bl = require('bl')

    http.get("http://www.website.", function (response) {
        response.pipe(bl(function (err, data) {
            if (err) {
                callback(err);
                return;
            }
            var data = data.toString()
            var description = { /* your description object */ }

            callback(description);
        }))
    })
}

exports.leboncoin = leboncoin;

var module = require('./leboncoin');

// -----------------vvvvvvvv
module.leboncoin(function(res) {
    console.log(res);
});

The method http.get requires a function that accepts only a parameter named response (or whatever you want, the name doesn't matter indeed), thus your second one, callback, is undefined and invoking it will end ever in that error.