javascript - How do you recursively remove nested objects that contain an empty array?

Question

I initially receive an AJAX response of {"B":{"1":"100","3":{"AA":256}},"A":100} and converted to a javascript object:

var jsonOBJ = {};
jsonOBJ = jQuery.parseJSON(data);

Future responses can be subsets or supersets of the initial response. If the value of a table is unchanged at the server, the stagnant data is replaced with an empty array. Example:

{"B":{"1":"90","2":200,"3":[]}}

{"B":[],"A":20}

Everytime an AJAX response is received, the object is updated with:

jQuery.extend(true, jsonOBJ, jQuery.parseJSON(data));

But I need the javascript object to keep the unchanged portions, so I need to end up with an object that would be equivalent to the following with the example responses above:

jsonOBJ = jQuery.parseJSON('{"B":{"1":"90","2":200,"3":{"AA":256}},"A":20}');

My preferred option would be to remove the empty objects from the converted response. Is there an existing function or a modification to the jQuery extend function that would do this?

Answer 1

You can remove the elements in your response with empty arrays with this code.

It cycles through the top level, looking for any empty arrays and removing them. Any objects it finds, it recurses into to also remove empty arrays in them:

// make sure the ES5 Array.isArray() method exists
if(!Array.isArray) {
  Array.isArray = function (arg) {
    return Object.prototype.toString.call(arg) == '[object Array]';
  };
}

function removeEmptyArrays(data) {
    for (var key in data) {
        var item = data[key];
        // see if this item is an array
        if (Array.isArray(item)) {
            // see if the array is empty
            if (item.length == 0) {
                // remove this item from the parent object
                delete data[key];
            }
        // if this item is an object, then recurse into it 
        // to remove empty arrays in it too
        } else if (typeof item == "object") {
            removeEmptyArrays(item);
        }
    }    
}

var jsonOBJ = {};
jsonOBJ = jQuery.parseJSON(data);
removeEmptyArrays(jsonOBJ);

You can see it work here: http://jsfiddle.net/jfriend00/U6qMH/