Merging two JS Objects into one

JS Object Merge

/**
 *  Merge two JS Objects
 *
 *  returns a new Object with values of
 *   first and second added to each other.
 *
 *  Note:
 *   Object items should only have integers for values
 *   ..otherwise, boom!
 */
var merge = function(first, second) {

    first = first || {};
    second = second || {};

    var item,

        // Clone the first object.
        //  We add the second's values to this.
        third = JSON.parse(JSON.stringify(first));

    // Loop through the object and add the values.
    for (item in second) {

        if (typeof second[item] === 'object') {
            // Recurse
            third[item] = merge(first[item], second[item]);
        } else {
            // remember: third is a clone of first.
            third[item] = third[item] || 0;
            third[item] += second[item];
        }

    }

    return third;

};



/////// THINGS!

var x = {
    x: 1,
    y: 1,
    foo: {
        bar: 1
    }
};
var y = {
    x: 2,
    y: 2,
    foo: {
        bar: 2
    }
};
var z = {
    x: 3,
    y: 3,
    foo: {
        bar: 3
    }
};

var things = [x, y, z];
var all = {};

// Reverse loop
for (var i = things.length - 1; i >= 0; i--) {
    console.log(all);
    all = merge(all, things[i]);
}