HTTP request callback on Node JS

Question

Hi I am trying to get a response via a http using the callback method. But I get an error saying callback is not a function.

 module.exports.ipLookup = function (res, callback) {
    var http = require('http');
    var str = '';
    var options = {
        host: 'ip-api.com',
        port: 80,
        path: '/json/',
        method: 'POST'
    };
    var str= "";
    var req = http.request(options, function (res) {
        res.on('data', function (body) {
            str += body;
        });

        res.on('end', function () {
            callback(str);
        });
    });


    req.end();

    return str;

    }

What is should to id return the json api response via ip-api.com. If anyone can help me on this it would be greatly appreciated.

How are you using/invoking ipLookup()? The value of callback will be determined there. — Jonathan Lonowski
– Jonathan Lonowski, Commented Nov 22, 2015 at 5:55
@JonathanLonowski, thanks for the reply. I am requiring the js file onto another file. e.g. var lookup = require('ip'); using lookup.ip(); — mattts
– mattts, Commented Nov 22, 2015 at 8:35

simon-p-r · Accepted Answer · 2015-11-23 16:05:53Z

4

In the other file you are loading the function from you need to ensure the callback parameter is used. See snippet below

var Lookup = require('./ip');
Lookup.ipLookup(function (response) {

    console.log(response) // check if response is valid
})

You need to change the exported function to only accept one parameter as the first parameter is not used inside function body like so.

module.exports.ipLookup = function (callback) {

    var http = require('http');
    var str = '';
    var options = {
        host: 'ip-api.com',
        port: 80,
        path: '/json/',
        method: 'POST'
    };

    var req = http.request(options, function (res) {

         res.on('data', function (body) {
             str += body;
         });

         res.on('end', function () {
             return callback(str);
         });
    });
    req.end();

}

edited Nov 23, 2015 at 16:05

answered Nov 22, 2015 at 11:40

simon-p-r

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4 Comments

mattts Over a year ago

thanks for this worked like a charm, one more question how do I make the "response" variable accessible out of the variable scope? Hope you can help me out on this. thanks

simon-p-r Over a year ago

Either hoist a variable which can be shared by other functions or exported to another module to be used. Or chain as part of a series of task and work on objects to achieve what you want to do? What do you want to do with the context?

mattts Over a year ago

what I want to do is in this case use the "response" as an array and break down the values and assign them to separately. Again thanks for the help

simon-p-r Over a year ago

Call the function with a control flow library and merge return values into your requirement. I use neo-async as haven't made switch to native promises yet!

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