Question

I was expecting the obj to be instanceof F1 (‘this’ in ‘this.prop’ refers to F1 object in the code snippet below, similarly I thought ‘this’ in ‘return this’ of C1 refers to F1 which is not the case. It refers to Global Window object), but in actuality it is an instanceof Window. Why is that ? could you please explain ?

function F1() {
  this.prop = 5;
  function C1() {
   return this;
  }
  return C1();
}
var obj = new F1();

Answer 1

if you are just creating an instance of F1, then just do this:

function F1() {
  this.prop = 5;
}
var obj = new F1();

you don’t need to return anything.

---

the this inside C1 is not the same as this outside it. if you want to preserve this of the outside so that C1 can use it, store it into another variable

function F1() {

    //preserve "this" from outside 
    var that = this;

    this.prop = 5;

    function C1() {
       return that; //"that" is "this" of the outside
    }
}