The arrow function does not work when I put it inside the object, the result after call is NaN [duplicate]

Question

var mySelf = {
  name: "dina",
  job: "Programmer",
  yearOfBirth: 1993,
  age: () => 2019 - this.yearOfBirth
};

let result = mySelf.age();

console.log(result);

the result is NaN

please help me what actually happened?

Answer 1

The arrow function inherit the enclosing context (that is Window in this case) rather then the object context, use a plain function instead.

var mySelf = {
  name: "dina",
  job: "Programmer",
  yearOfBirth: 1993,
  age: function() { return 2019 - this.yearOfBirth }
};
    
let result = mySelf.age();
    
console.log(result);

To show that an arrow function receives a lexical this -

const o =
  { func: () => this === window }
  
console.log(o.func()) // true

Answer 2

If use the name mySelf instead of this(because it will not reference the object in this case) to reference your object it seems to work fine.

var mySelf = {
  name: "dina",
  job: "Programmer",
  yearOfBirth: 1993,
  age: () => 2019 - mySelf.yearOfBirth
};

let result = mySelf.age();

console.log(result);