I have a JSON string from an API response which looks like this:

{ "legend_size": 1,
  "data": {
    "series": [ "2013-05-01", "2013-05-02" ],
    "values": {
        "Sign Up": {
            "2013-05-05": 10,
            "2013-05-04": 10
         }
     }
  }
}

I'd like to sum the values in the "Sign Up" Object (10 + 10). The challenge I am having is that the key's are unique and most of the posts demonstrating how to do something like this show examples where it is just an array of values or the keys are consistent (ie - every key is "value").

Should I be attempting to use the Series array to loop through the Sign Up Object?

I have a JSON string from an API response which looks like this:

{ "legend_size": 1,
  "data": {
    "series": [ "2013-05-01", "2013-05-02" ],
    "values": {
        "Sign Up": {
            "2013-05-05": 10,
            "2013-05-04": 10
         }
     }
  }
}

I'd like to sum the values in the "Sign Up" Object (10 + 10). The challenge I am having is that the key's are unique and most of the posts demonstrating how to do something like this show examples where it is just an array of values or the keys are consistent (ie - every key is "value").

Should I be attempting to use the Series array to loop through the Sign Up Object?

• javascript
• arrays
• json
• object
• addition

• forgot to mention, my first step in trying to solve this was to use JSON.parse(string); to put it in to a JS Object. Not sure if that is necessary. – nielsfogt Commented Jun 10, 2013 at 1:53

2 Answers 2

Assuming you've already got your data parsed into an object, you can use a for loop like this:

var json = {
    "legend_size": 1,
    "data": {
        "series": [ "2013-05-01", "2013-05-02" ],
        "values": {
            "Sign Up": {
                "2013-05-05": 10,
                "2013-05-04": 10
            }
        }
    }
};
var sum = 0;
for (x in json.data.values['Sign Up']) {
    sum += json.data.values['Sign Up'][x];
}

Basically, we navigate through the json data to get the the actual data that we want... which is the 'Sign Up' object. Then we use a for/in loop to loop through all the keys that that object has, and add up the values.

After you've parsed it, here's a way to arrive at the sum by using Array.prototype.reduce.

var vals = object.data.values["Sign Up"];

var result = Object.keys(vals)
                   .reduce(function(sum, key) {
                       return sum + vals[key]
                   }, 0);

The .reduce() and .keys() methods will need shims for IE8 and lower.