Creating a JSON Array in node js

Question

I need to create in my server written in node js a JSON string to be sent to the client when this request it. The problem is that this JSON depends on the available data in the server, thus, the size of the JSON array is not the same always. I´ve trying whole day but although I feel to be close I still dont get it.

An example query follows:

json={"players":[
            {"name":"Messi", "goals":8},            
            {"name":"Ronaldo", "goals":22},
            {"name":"Costa", "goals":20},
            {"name":"Neymar", "goals":13},
            {"name":"Arabi", "goals":6},
            {"name":"Bale", "goals":3},
            {"name":"Toquero", "goals":0}]};

I would send it to the server by:

res.contentType('application/json');
res.send(json);

The JSON array that I want create it depends on a hash called 'goals' where a player name is the key and a number of goals the value. Thus, if there are only 3 players, the JSON Array only should have this size.

I´ve been trying to create the JSON array online like this:

result= "";
for(i in goals){
    result = result+ '{ name:' + i + ", goals:" + goals[i] + '},';
}
result= result.substring(0, result.length - 1); 
res.contentType('application/json');
res.send( { 'players': [ result]});

However, the client only receives a json of size 1

Object {jugadores: Array[1]}

jugadores: Array[1] 0: "{ nombre:Messi, goles:8},{ nombre:Ronaldo, goles:16},{ nombre:Costa, goles:10},{ nombre:Toquero, goles:0},{ nombre:Arabi, goles:2},{ nombre:Bale, goles:10},{ nombre:Neymar, goles:8}" length: 1

Thanks in advance, Im really struggling with this :(

Edit: Im trying now with stringy doing this, but no luck. What do I do wrong?

result= "players:[";
for(i in goals){
    result= result+ '{ name:' + i + ", goals:" + goals[i] + '},';
}

result= result.substring(0, resultado.length - 1);  
result= result + ']'

res.contentType('application/json');
myJSONstring = JSON.stringify(resultado);
res.send(myJSONstring);

Goals hash is filled using GET:

app.get('/player/:id', function (req, res) {   
res.contentType('application/json');
res.send( {'goals': + goals[req.params.id] } );

});

use res.send(JSON.stringify(players)) and get rid of the loop and result variable. — Zeeshan Abbas, Dec 08 '13 at 23:52
how? I mean, if I get rid of the loop I dont obtain the information that I want to send. — Rafag, Dec 08 '13 at 23:56
can you show the part of your code where you are setting the value of `goals` — Zeeshan Abbas, Dec 08 '13 at 23:59
possible duplicate of [Convert JS object to JSON string](http://stackoverflow.com/questions/4162749/convert-js-object-to-json-string) — Felix Kling, Dec 09 '13 at 00:02
You are supposed to pass an object or array to `JSON.stringify`, not a string. — Felix Kling, Dec 09 '13 at 00:14

score 46 · Accepted Answer · edited Dec 09 '13 at 00:13

Build up a JavaScript data structure with the required information, then turn it into the json string at the end.

Based on what I think you're doing, try something like this:

var result = [];
for (var name in goals) {
  if (goals.hasOwnProperty(name)) {
    result.push({name: name, goals: goals[name]});
  }
}

res.contentType('application/json');
res.send(JSON.stringify(result));

or something along those lines.

score 8 · Answer 2 · answered Dec 08 '13 at 23:49

8

You don't have JSON. You have a JavaScript data structure consisting of objects, an array, some strings and some numbers.

Use JSON.stringify(object) to turn it into (a string of) JSON text.

answered Dec 08 '13 at 23:49

Quentin

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Ive tried to create the JavaScript data structure and use stringify (check my edit please) but no luck, what am I missing? – Rafag Dec 09 '13 at 00:07
1

You're trying to construct your data structure by gluing together strings representing JS literals. Use actual literals. – Quentin Dec 09 '13 at 00:14

score 4 · Answer 3 · answered Jul 04 '16 at 09:03

This one helped me,

res.format({
        json:function(){
                            var responseData    = {};
                            responseData['status'] = 200;
                            responseData['outputPath']  = outputDirectoryPath;
                            responseData['sourcePath']  = url;
                            responseData['message'] = 'Scraping of requested resource initiated.';
                            responseData['logfile'] = logFileName;
                            res.json(JSON.stringify(responseData));
                        }
    });

Creating a JSON Array in node js

3 Answers3

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