parsing nested json object

Question

I have a json file that I'm trying to get values out of. One object is nested inside another in this file. I can isolate the top level values, but not the nested values. It must be a syntax issue. Here's what I'm using.

This is the json:

{
    "total": [
        [
            {
                "votes": "79,060"
            },
            {
                "percent": "11%"
            },
            {
                "winner": "0"
            }
        ],
        [
            {
                "votes": "167,800"
            },
            {
                "percent": "22%"
            },
            {
                "winner": "0"
            }
        ],
        [
            {
                "votes": "51,519"
            },
            {
                "percent": "7%"
            },
            {
                "winner": "0"
            }
        ],
        [
            {
                "votes": "297,060"
            },
            {
                "percent": "39%"
            },
            {
                "winner": "1"
            }
        ],
        [
            {
                "votes": "156,787"
            },
            {
                "percent": "21%"
            },
            {
                "winner": "0"
            }
        ]
    ],
    "useWinnerColors": 1,
    "timestamp": "3:00 p.m. April 26",
    "candidateCount": 5
}

When I write:

console.log(json.candidateCount);

I get the right answer (5).

But when I write:

console.log(json.total[0][1]);

I get Object { percent="11%"}.

And when I write:

console.log(json.total[0].votes);

I get undefined.

How do I isolate the value of the items in "total", please?

That is some strangely-constructed JSON. Why is total an array of 3-element arrays, each of which contains a one-element object, instead of total being an array of objects? — Matt Ball
– Matt Ball, Commented Jun 29, 2012 at 17:37
This is actually a snippet of a larger json file that has totals for each county. — LauraNMS
– LauraNMS, Commented Jun 29, 2012 at 17:39

Vivin Paliath · Accepted Answer · 2012-06-29 17:58:17Z

6

You're getting undefined because json.total[0] is itself, an array. You need to isolate the specific array inside json.total[0]. So you would need to do something like json.total[0][0].votes or json.total[0][1].votes.

I think a better structure for your JSON would be something like this:

{"total": [    
   {
      "votes": "79,060"
      "percent": "11%"
      "winner": "0",
   },
   ...
   {
      "votes": "156,787",
      "percent": "21%",
      "winner": "0"
   }], 
   "useWinnerColors": 1,
   "timestamp": "3:00 p.m. April 26",
   "candidateCount": 5
}

Now you can do json.total[0].votes.

You don't need to create an array where each entry is a name-value pair. You can directly use an associative-array.

EDIT: To iterate over your associative array, use for..in along with hasOwnProperty(). The hasOwnProperty() check will prevent you from iterating over properties that it has inherited (some third-party libraries pollute the namespace):

var map = json.total[0];
for(var prop in map) if(map.hasOwnProperty(prop)) {
   var value = map[prop];
   ...
}

edited Jun 29, 2012 at 17:58

answered Jun 29, 2012 at 17:36

Vivin Paliath

95.8k42 gold badges230 silver badges302 bronze badges

Sign up to request clarification or add additional context in comments.

5 Comments

LauraNMS Over a year ago

What if I don't know the name of the child node ("votes")? I see I can't use json.total[0][0][0]. How would I indicate that node?

raina77ow Over a year ago

Than you're trying to use hash without knowing its key, and it's not right. ) Strictly speaking, order of properties in object is not guaranteed, so even some imitation of iterating over them (with var p in o loop) will probably fail. And [0][0][0] is just not correct.

Vivin Paliath Over a year ago

As raina77ow said, you should know the name. After all, you're the one who populated the hash :) If you don't know the name, what you can do is iterate over them. Although order is not guaranteed, you can access each property and its value. Check out my edit.

Kristen Grote Over a year ago

@VivinPaliath Where did map and prop come from? I'm trying to do something pretty similar but I'm not sure what values I need to put where.

Vivin Paliath Over a year ago

@kgrote map and prop are just variable names that I used.

raina77ow · Accepted Answer · 2012-06-29 17:37:42Z

3

Each '[' symbol means we deal with Array, each '{' - with Object. So json.total is actually an array of arrays of objects (though each inner object is just a 'tuple' - single key-value pair.

So...

json.total[0][1] - evaluates to { 'percent': '11%' }

json.total[0]['votes'] - evaluates to nothing (undefined), as one step is skipped. ) It really should be json.total[0][n].votes or json.total[0][n]['votes']. These two forms are (almost) identical. )

answered Jun 29, 2012 at 17:37

raina77ow

107k16 gold badges205 silver badges240 bronze badges

Collectives™ on Stack Overflow

parsing nested json object

2 Answers 2

5 Comments

Comments

Your Answer

Linked

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

5 Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Linked

Related