dumb dirty way to find if an object key exists in a deep object

gistfile1.js

keyExists = function(obj, structure) {

    var F = function(){};
    F.prototype = obj;

    var parts = structure.split('.');
    var testObj = new F;

    for (var i = 0, j = parts.length; i < j; i++) {
        if (!testObj[parts[i]]) {
            return false;
        } else {
            testObj = testObj[parts[i]];
        }
    }

    return true;
}


var obj = {
    a : {
        b : {
            c : {
                d : {
                    e : {
                        f : {
                            g : {
                                h : {
                                    i : 333
                                }
                            }
                        }
                    }
                }
            }
        }
    }
};

console.assert(keyExists(obj, 'a.b.c.d.e.f.g.h.i'));

console.assert( ! keyExists(obj, 'a.b.c.d.e.f.g.h.i.j.k') );