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

function* gen() {
  yield 1;
  yield 2;
  return 3;
}
const g = gen();
console.log([...g]);

const nums = [1, 2, 3];
const res = nums.reduce((acc, val) => acc + val, "");
console.log(typeof res);

(async function() {
  return await 10;
})().then(console.log);

function foo() {}
foo.prototype.bar = 42;
const obj = new foo();
foo.prototype = { bar: 100 };
console.log(obj.bar);

const obj = {
  0: "zero",
  1: "one",
  length: 2
};
console.log(Array.from(obj));

const map = new Map();
map.set("key", undefined);
console.log(map.has("key"), map.get("key"));