Arrow notation in init function

[giper45]

Thanks for this wonderful library ! Just I little question (for curiosity), why when I use arrow function notation in init function it gives empty object on instantiation ? I.e with normal notation:

// Some privileged methods with some private data.
const Availability = stampit().init(function() {
  var isOpen = false; // private

  this.open = function open() {
    isOpen = true;
    return this;
  };  
  this.close = function close() {
    isOpen = false;
    return this;
  };  
  this.isOpen = function isOpenMethod() {
    return isOpen;
  }
});
console.log(Availability())

>> { open: [Function: open],
  close: [Function: close],
  isOpen: [Function: isOpenMethod] }

while the arrow notation gives this :

// Some privileged methods with some private data.
const Availability2 = stampit().init(() => {
  var isOpen = false; // private

  this.open = function open() {
    isOpen = true;
    return this;
  };  
  this.close = function close() {
    isOpen = false;
    return this;
  };  
  this.isOpen = function isOpenMethod() {
    return isOpen;
  }
});
console.log(Availability2()) 

>> {}

Thanks !

[amelon]

arrow functions are some kind special. They are bound to their outside context and cannot be bound to your stamp instance.

Don't use fat arrow function with init method.

[koresar]

Thanks @amelon ! I'll put some code examples for @giper45

const outerObject = {
  name: "outerObject",

  f1: function() { // <---------- regular function
    console.log(this); 

    const innerObject = {
      name: "innerObject",
      f2: () => { // <---------- arrow function
        console.log(this);
      }
    };

    innerObject.f2();
  }
};

outerObject.f1();

The code above will print:

{ name: 'outerObject', f1: [Function: f1] }
{ name: 'outerObject', f1: [Function: f1] }

It prints the same object! Why? Because arrow functions (f2) INHERIT the this context of the running function (f1).

---

There is a way to use arrow functions as initializers. Here it is:

const Availability2 = stampit().init((_, {instance}) => {

  instance.open = function open() { }; // See this `instance` variable?
  // ...
});

If any questions feel free to ask.

[giper45]

Thanks very much for the explanation !!! I've learned something more about Javascript in general :) !