Why is the constructor changed?

Question

Why does the constructor change from Foo to Object after adding a prototype? How can I get access to the original constructor?

Code:

function Foo() {}
var foo1 = new Foo();
console.log('foo1: ' + foo1.constructor);

Foo.prototype = {}
var foo2 = new Foo();
console.log('foo2: ' + foo2.constructor);

Output:

foo1: function Foo() {}

foo2: function Object() {
    [native code]
}

http://jsfiddle.net/vDCTJ/

Answer 1

It happens because you gave Foo a brand new object for its prototype, and you didn't set that object's "constructor" property.

Foo.prototype = { constructor: Foo };

Instantiated function objects get an object for their "prototype" property that's already initialized that way.