Experimenting with deep merge leveraging prototypal inheritance instead of pure JSON objects for YCB

deep-merge.js

function heir (o) {
    function F() {}
    F.prototype = o;
    return new F();
}

function heirDeep (o) {

    var dest,
        i;

    dest = heir(o);

    for (i in o) {
        if (o.hasOwnProperty(i) && o[i] && typeof o[i] === 'object') {
            dest[i] = heirDeep(o[i]);
        }
    }

    return dest;
}

function heirDeepMerge (o, overlay) {

    var dest,
        i;

    overlay = overlay || {};

    dest = heir(o);

    for (i in o) {
        if (overlay.hasOwnProperty(i) && typeof overlay[i] !== 'object') {
            dest[i] = overlay[i]; // null, undefined, overruling an obj with a value, etc
        } else if (o.hasOwnProperty(i) && o[i] && typeof o[i] === 'object') {
            dest[i] = heirDeepMerge(o[i], overlay[i]);
        } else if (overlay.hasOwnProperty(i)) {
            dest[i] = overlay[i];
        }
    }

    return dest;
}

function merge (heir, overlay) {

    var i;

    overlay = overlay || {};

    for (i in heir) {
        if (overlay.hasOwnProperty(i) && typeof overlay[i] !== 'object') {
            heir[i] = overlay[i]; // null, undefined, overruling an obj with a value, etc
        } else if (heir[i] && typeof heir[i] === 'object') {
            heir[i] = merge(heir[i], overlay[i]);
        } else if (overlay.hasOwnProperty(i)) {
            heir[i] = overlay[i];
        }
    }

    return heir;
}




var from = {a: 1, b: 2, c: { d: 3 }};
var to = {a: 'a', c: {e: 4} };

var b = {c: 1};

var test1 = heir({
    a: 1,
    b: heir(b)
});

console.log('A: ', test1.a, test1.b.c, b.c);

test1.a = 2;
test1.b.c = 2;

console.log('B: ', test1.a, test1.b.c, b.c);





var origin = {
    a: 1,
    b: {c: 1}
};

var test2 = heirDeep(origin);

console.log('C: ', test2.a, test2.b.c, origin.b.c);

test2.a = 2;
test2.b.c = 2;

console.log('D: ', test2.a, test2.b.c, origin.b.c);





var base = {
    a: 1,
    b: {c: 1}
};
var overlay = {
    a: 2,
    b: {
        c: 2
    }
};

var test3 = heirDeepMerge(base, overlay);

console.log('E: ', test3.a, test3.b.c, base.b.c);





var cacheable = {
    a: 1,
    b: {c: 1}
};
var secure = {
    a: 2,
    b: {
        c: 2
    }
};

var test4 = merge(heirDeep(cacheable), secure);

console.log('F: ', test4.a, test4.b.c, cacheable.b.c);
test4.b.c = 3;
console.log('G: ', test4.b.c, cacheable.b.c, secure.b.c);