let obj = { a: 1 };
let proto = { b: 2 };

Object.setPrototypeOf(obj, proto);

for (let key in obj) {
  console.log(key);
}

let obj = { a: 1 };
Object.freeze(obj);

console.log(Object.isFrozen(obj));
console.log(obj.a = 2);
console.log(obj.a);

let obj = {};
Object.defineProperty(obj, 'a', {
  value: 1,
  enumerable: true
});

let clone = Object.create(
  Object.getPrototypeOf(obj),
  Object.getOwnPropertyDescriptors(obj)
);

console.log(clone.a);
console.log(clone.hasOwnProperty('a'));

let proto = { a: 1 };
let obj = Object.create(proto);

Object.defineProperty(obj, 'a', {
  value: 2,
  writable: false,
  enumerable: true,
  configurable: false
});

console.log(obj.a);
proto.a = 3;
console.log(obj.a);

console.log(1);

setTimeout(() => {
  console.log(2);
}, 100);

setTimeout(() => {
  console.log(3);
}, 0);

Promise.resolve().then(() => {
  console.log(4);
}).then(() => {
  console.log(5);
});

console.log(6);

const obj = {
  a: 1,
  b: function() {
    return () => {
      return this.a;
    };
  },
  c: function() {
    return function() {
      return this.a;
    };
  }
};

const arrowFunc = obj.b();
const regularFunc = obj.c();

console.log(arrowFunc());
console.log(regularFunc());

function* generator() {
  yield* [1, 2, 3];
  yield 4;
}

const gen = generator();
console.log([...gen]);