How can I see a Javascript object's prototype chain?

Question

Given the following code:

function a() {}
function b() {}
b.prototype = new a();
var b1 = new b();

We can stay that a has been add

Answer 1

Well, the prototype link between objects ([[Prototype]]) is internal, some implementations, like the Mozilla, expose it as obj.__proto__.

The Object.getPrototypeOf method of the ECMAScript 5th Edition is what you're needing, but it isn't implemented right now on most JavaScript engines.

Give a look to this implementation by John Resig, it has a pitfall, it relies on the constructor property of engines that don't support __proto__:

if ( typeof Object.getPrototypeOf !== "function" ) {
  if ( typeof "test".__proto__ === "object" ) {
    Object.getPrototypeOf = function(object){
      return object.__proto__;
    };
  } else {
    Object.getPrototypeOf = function(object){
      // May break if the constructor has been tampered with
      return object.constructor.prototype;
    };
  }
}

Remember that this is not 100% reliable, since the constructor property is mutable on any object.