How to build JSON object with nested JSON objects

Question

I am constructing a JSON object with nested objects in Javascript. Is there an easy way to do this in Javascript without using eval()?

var data_json = "data = {'"+field_name+"':{'answers':{";
for(var i=0; i<answers.length; i++){
    data_json += "'" + i + "':" + "'" + answers[i] + "',";
}
data_json = data_json.replace(/,$/,"");
data_json = data_json + "}}}";

eval(data_json);

Result:

data={'myfield':{'answers':{'0':'The answer', '1':'Another answer'}}};

why are you constructing json in javascript, javascript IS json — dstarh
– dstarh, Commented Apr 13, 2012 at 15:55
I'm not sure what you mean. JSON is "JavaScript Object Notation". It is a language-independent data interchange format. — Stephen305
– Stephen305, Commented Apr 13, 2012 at 16:10
Correct i should have expanded on what i was saying. JavaScript objects are json, there's no need to use string concat just build the object graph as is done in the selected answer — dstarh
– dstarh, Commented Apr 13, 2012 at 18:03

Fabrizio Calderan · Accepted Answer · 2012-04-13 16:02:05Z

4

var a, data = {};
data[field_name] = { "answers" : { } };
a = data[field_name]["answers"];

for(var i=0; i<answers.length; i++){
   a[i] = answers[i];
}


console.log(data);

As a side note, if data[field_name]["answers"] contains numeric keys only, it should be an array and not an object, so data[field_name] should be = { "answers" : [ ]};

edited Apr 13, 2012 at 16:02

answered Apr 13, 2012 at 15:56

Fabrizio Calderan

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RoboKozo · Accepted Answer · 2012-04-13 15:57:33Z

3

Personally, I'd use JSON.stringify to convert your javascript objects into a json string format.

Check these out for more information.

http://msdn.microsoft.com/en-us/library/cc836459(v=vs.85).aspx

https://developer.mozilla.org/en/JavaScript/Reference/Global_Objects/JSON/stringify

You can also use JSON.parse to go the other way (from string to object)

var myObject = JSON.parse(myJSONtext, reviver);

http://www.json.org/js.html

answered Apr 13, 2012 at 15:57

RoboKozo

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