// Let's create an object o from function f with its own properties a and b:
let f = function () {
   this.a = 1;
   this.b = 2;
}
let o = new f(); // {a: 1, b: 2}

// add properties in f function's prototype
f.prototype.b = 3;
f.prototype.c = 4;

// do not set the prototype f.prototype = {b:3,c:4}; this will break the prototype chain
// o.[[Prototype]] has properties b and c.
// o.[[Prototype]].[[Prototype]] is Object.prototype.
// Finally, o.[[Prototype]].[[Prototype]].[[Prototype]] is null.
// This is the end of the prototype chain, as null,
// by definition, has no [[Prototype]].
// Thus, the full prototype chain looks like:
// {a: 1, b: 2} ---> {b: 3, c: 4} ---> Object.prototype ---> null

console.log(o.a); // 1
// Is there an 'a' own property on o? Yes, and its value is 1.

console.log(o.b); // 2
// Is there a 'b' own property on o? Yes, and its value is 2.
// The prototype also has a 'b' property, but it's not visited.
// This is called Property Shadowing

console.log(o.c); // 4
// Is there a 'c' own property on o? No, check its prototype.
// Is there a 'c' own property on o.[[Prototype]]? Yes, its value is 4.

console.log(o.d); // undefined
// Is there a 'd' own property on o? No, check its prototype.
// Is there a 'd' own property on o.[[Prototype]]? No, check its prototype.
// o.[[Prototype]].[[Prototype]] is Object.prototype and there is no 'd' property by default, check its prototype.
// o.[[Prototype]].[[Prototype]].[[Prototype]] is null, stop searching