Clone an Object with all its circular references. Take that jQuery.extend!

clone_object_with_circular_references.js

function cloneObject(object) {
    return extendObject({}, object);
}

function extendObject(base, object) {
    var visited = [object];

    // http://en.wikipedia.org/wiki/Adjacency_list_model
    var set = [{value: base}];

    _extend(base, object);
    return base;

    function _extend(base, object) {
        for (var key in object) {
            var value = object[key];
            if (typeof value === 'object') {
                var index = visited.indexOf(value);
                if (index === -1) {
                    visited.push(value);
                    var newBase = base[key] = {};
                    set.push({up: base, value: newBase});
                    _extend(newBase, value);
                } else {
                    base[key] = set[index].value;
                }
            } else {
                base[key] = value;
            }
        }
    }
}


// Example #1
var a = {};
a.self = a;
console.log(a, cloneObject(a));


// Example #2
var b = {
    x: 1,
    y: {
        y1: 2,
        z1: {
            z2: 3
        }
    }
};
b.top = b;
b.y.top = b;
b.y.z1.top = b;
b.y.up = b;
b.y.z1.up = b.y;
b.y.z1.self = b.y.z1;

var bClone = cloneObject(b);
bClone.x = 42;
bClone.y.y1 = 13;
console.log(b, bClone);