Question

Can we get lookup count for object3.x?

First – look into owned property – no x

Second – look into prototype object of object3 ->object2 – no x

Third – look into prototype object of object2 -> object 1 – x defined – yes

object1 = {x:1};
object2 = Object.create(object1);
object2.y = 2;
object3 = Object.create(object2);
object3.z = 3;

object1.x; // lookup count = 1
object2.x; // lookup count = 2
object3.x; // lookup count = 3

Answer 1

You could create a function for that purpose…

function prop_depth(obj, p) {
    var count = 1;

    while(obj && !obj.hasOwnProperty(p)) {
        obj = Object.getPrototypeOf(obj);
        count++; 
    }
    return obj ? count : -1;
}

prop_depth(object1,'x'); // lookup count = 1
prop_depth(object2,'x'); // lookup count = 2
prop_depth(object3,'x'); // lookup count = 3