Question

(forgive me if I use slightly incorrect language – feel free to constructively correct as needed)

There are a couple posts about getting data from JSON data of siblings in the returned object, but I’m having trouble applying that information to my situation:

I have a bunch of objects that are getting returned as JSON from a REST call and for each object with a node of a certain key:value I need to extract the numeric value of a sibling node of a specific key. For example:

For the following list of objects, I need to add up the numbers in “file_size” for each object with matching “desc” and return that to matching input values on the page.

{"ResultSet":{

  Result":[

    {
        "file_size":"722694",
        "desc":"description1",
        "format":"GIF"
    },

    {
        "file_size":"19754932",
        "desc":"description1",
        "format":"JPEG"
    },

    {
        "file_size":"778174",
        "desc":"description2",
        "format":"GIF"
    },

    {
        "file_size":"244569996",
        "desc":"description1",
        "format":"PNG"
    },

    {
        "file_size":"466918",
        "desc":"description2",
        "format":"TIFF"
    }

  ]

}}

Answer 1

You can use the following function:

function findSum(description, array) {
    var i = 0;
    var sum = 0;

    for(i = 0; i < array.length; i++) {
        if(array[i]["desc"] == description && array[i].hasOwnProperty("file_size")) {
            sum += parseInt(array[i]["file_size"], 10);
        }
    }

    alert(sum);
}

And call it like this:

findSum("description1", ResultSet.Result);

To display an alert with the summation of all "description1" file sizes.

A working JSFiddle is here: http://jsfiddle.net/Q9n2U/.

---

In response to your updates and comments, here is some new code that creates some divs with the summations for all descriptions. I took out the hasOwnProperty code because you changed your data set, but note that if you have objects in the data array without the file_size property, you must use hasOwnProperty to check for it. You should be able to adjust this for your jQuery .each fairly easily.

var data = {};
var array = ResultSet.Result;

var i = 0;
var currentDesc, currentSize;
var sizeDiv;
var sumItem;

//Sum the sizes for each description
for(i = 0; i < array.length; i++) {
    currentDesc = array[i]["desc"];
    currentSize = parseInt(array[i]["file_size"], 10);

    data[currentDesc] =
        typeof data[currentDesc] === "undefined"
        ? currentSize
        : data[currentDesc] + currentSize;
}

//Print the summations to divs on the page
for(sumItem in data) {
    if(data.hasOwnProperty(sumItem)) {
        sizeDiv = document.createElement("div");
        sizeDiv.innerHTML = sumItem + ": " + data[sumItem].toString();
        document.body.appendChild(sizeDiv);
    }
}

A working JSFiddle is here: http://jsfiddle.net/DxCLu/.