Javascript constructor return values [duplicate]

Question

Consider the following code:

function Foo() {
  return "something";
}

var foo = new Foo(); 

According to the experts in JavaScript, they say that return "nothing" or just "this" from a constructor. Whats the reason for this?

I am aware that when used "new", the "this" would be set to the prototype object of the constructor but not able to understand this point alone.

Answer 1

That particular code will throw a ReferenceError because something is not declared.

You should either return this or have no return statement at all in a constructor function because otherwise you will have constructed a new instance of the class (the value of this, and the default return value) and then thrown it away.

I am aware that when used "new", the "this" would be set to the prototype object of the constructor

Incorrect. It will be set to an instance of the constructor.