const func = () => arguments.length;
console.log(func(1, 2, 3));

const array = Array.from({ length: 5 }, () => Math.random() > 0.5);

console.log(array);

const obj1 = { a: 1 };
const obj2 = Object.create(obj1);
obj2.b = 2;

const result = 'a' in obj2;

console.log(result);

const array = [1, 2, 3];
array[-1] = 0;

console.log(array.length);

const obj = {
  a: 1,
  then(resolve) {
    resolve(this.a);
  }
};

obj.then(console.log);

const array = [1, 2, 3];
const obj = { a: 1, b: 2 };

array.push(obj);
obj.a = 3;

console.log(array[3].a);