Access keys from the object where the method is being declared in JavaScript

Question

I would like to know why this example shows the following behavior. If we write:

let person = {
  name: 'ENoy',
  age: 25,
  weekendAlarm: 'No alarms needed',
  weekAlarm: 'Alarm set to 7AM',
  sayHello: () => {
    return `Hello, my name is ${this.name}`;
  },
  sayGoodbye(){
    return 'Goodbye!';
    }
};

console.log(person.sayHello());

let friend = {
  name: 'Bruno'
};

friend.sayHello = person.sayHello;

console.log(friend.sayHello());

We get as output:

Hello, my name is undefined
Hello, my name is undefined

And if we try to use:

let person = {
  name: 'ENoy',
  age: 25,
  weekendAlarm: 'No alarms needed',
  weekAlarm: 'Alarm set to 7AM',
  sayHello: () => {
    return `Hello, my name is ${person.name}`;
  },
  sayGoodbye(){
    return 'Goodbye!';
    }
};

console.log(person.sayHello());

let friend = {
  name: 'Tori'
};

friend.sayHello = person.sayHello;

console.log(friend.sayHello());

We see:

Hello, my name is ENoy
Hello, my name is ENoy

In Java I have seen various ways to get it done:

Java - get the current class name?

In JavaScript I have seen the constructor:

Get name of object or class

But I think in the previous link we get the method which instantiated the object we would like in this topic get the variable from the object where the function is declared.