prototype, __proto__ & constructor in JS

gistfile1.js

var Foo1 = function() {};
var Foo2 = function() {};
var foo1 = new Foo1();    

console.log(foo1.constructor == Foo1.prototype.constructor) // true
console.log(Foo1.prototype.constructor == Foo1) // true
console.log(foo1.constructor == Foo1) // true
console.log(foo1.constructor == foo1.__proto__.constructor) // true
console.log(foo1.__proto__.constructor == Foo1) // true

Foo1.prototype = new Foo2();

console.log('');
console.log(foo1.constructor == Foo1.prototype.constructor) // false
console.log(Foo1.prototype.constructor == Foo1) // false
console.log(foo1.constructor == Foo1) // true
console.log(foo1.constructor == foo1.__proto__.constructor) // true
console.log(foo1.__proto__.constructor == Foo1) // true
console.log('');

var foo3 = new Foo1();

console.log(foo3.__proto__.constructor == foo1.__proto__.constructor) // false
console.log(foo3.__proto__.constructor == Foo2) // true
console.log(foo3.__proto__ == Foo1.prototype); // true