The deep copy is implemented in the same way as the shallow copy: you loop through the properties and copy them one by one. But, when you encounter a property that points to an object, you call the deep copy function again:

function deepCopy(p, c) {
    c = c || {};
    for (var i in p) {
        if (p.hasOwnProperty(i)) {
            if (typeof p[i] === 'object') {
                c[i] = Array.isArray(p[i]) ? [] : {};
                deepCopy(p[i], c[i]);
            } else {
                c[i] = p[i];
            }
        }
    }
    return c;
}

Usage :

> var mydeep = deepCopy(parent);