JSON loop a multidimensional array to with node.js

Question

Having read up on different methods please bear with me to try to explain.

I am trying to retreive data from the twitch api and loop the user.name results to an array possibly inside an object. I am using nodejs so it has to be javascript.

So far when I run the following I get a nice json response.

var request = require('request');

    request({url: 'https://api.twitch.tv/kraken/channels/twitch/follows?limit=3'}, function(err, res, json) {
        if (err) {
            throw err;
        }

        console.log(json);

    });

this then logs the same as if one where to visit https://api.twitch.tv/kraken/channels/twitch/follows?limit=3

or better visualized as

json structure

Now I want to select the follows -> user -> name object. More so, loop every user -> name in the response.

I thought I would need to convert the string to an object so I tried

    var obj = JSON.parse(json);

but that only returns the first {3} objects in the tree. So I went ahead and tried

var request = require('request');

    request({url: 'https://api.twitch.tv/kraken/channels/twitch/follows?limit=3'}, function(err, res, json) {
        if (err) {
            throw err;
        }

        for (var i=0; i<json.length; i++) {

        var obj = JSON.parse(json.follows[i].user.name);
        console.log(obj);

        }

    });

and it returns

TypeError: Cannot read property '0' of undefined

For testing purposes I also got rid of the loop and just have 1 to return one bit of info. Having tried multiple instances of rearranging the call I always get either an error or "undefined" back.

Nothing seems to work, I am even going about this the right way?

tymeJV · Accepted Answer · 2015-07-21 19:48:44Z

2

Loop over json.followers.length - not json.length - json is an object, and objects don't have a length:

for (var i=0; i<json.follows.length; i++) {

edited Jul 21, 2015 at 19:48

answered Jul 21, 2015 at 19:40

tymeJV

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4 Comments

Lansana Camara Over a year ago

So simple yet so effective.

ServerSideSkittles Over a year ago

I seem to get TypeError: Cannot read property 'length' of undefined when trying this.

ServerSideSkittles Over a year ago

full edit : for (var i=0; i<json.follows.length; i++) { var obj = JSON.parse(json.user[i].name); console.log(obj); }

ServerSideSkittles Over a year ago

Thanks for your help, I marked the below question as the accepted answer. Not sure on the procedure but the extra line helped me even though its pretty much the same thing. Hope this is ok, I upvoted your question.

jrath · Accepted Answer · 2015-07-21 19:54:39Z

1

As json is an object here, we should use for-in though there is no length property. But here json.follows is an array. So we should use for loop.

var len = json.follows.length;
for (var i=0; i< len; i++) {
    console.log(json.follows[i].user.name);
}

edited Jul 21, 2015 at 19:54

answered Jul 21, 2015 at 19:48

jrath

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5 Comments

tymeJV Over a year ago

follows is an array - use a regular for loop for arrays.

jrath Over a year ago

yes...for follows we can use a regular for loop. But for json which is an object we should use for..in. I will update my answer.

ServerSideSkittles Over a year ago

I get TypeError: Cannot read property 'length' of undefined, the same as the above answer. Not sure how this is happening?

jrath Over a year ago

But I tested and its working fine. Can you do a console.log(json) and check what is the output and does it contains "follows" or not?

ServerSideSkittles Over a year ago

Yes I needed to include obj = JSON.parse(json); which then solved the issue. many thanks you :)

user3574474 · Accepted Answer · 2015-07-21 20:07:05Z

0

Supposing you do var obj = JSON.parse(json);

for (var j = 0; j < obj.follows.length; j++) {
    var thisName = jsonObj.follows[j].user.name;
    console.log(thisName);
}

answered Jul 21, 2015 at 20:07

user3574474

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