const map = new Map();
const key1 = {};
const key2 = key1;

map.set(key1, "Value for key1");
map.set(key2, "Value for key2");

console.log(map.get({}));
console.log(map.get(key1));

console.log(typeof NaN);
console.log(NaN === NaN);

const numbers = [1, 2, 3, 4, 5];
const result = numbers.map(num => {
    if (num === 3) {
        return num * 2;
    }
    return num;
});

console.log(result);

const obj = { a: 10 };
console.log(obj.a && obj.b || 20);

const arr = [1, 2, 3];
const copy = [...arr];
copy.push(4);

console.log(arr);
console.log(copy);

const obj = {
  a: 1,
  a: 2,
  a: 3
};
console.log(obj.a);

Number.prototype[Symbol.iterator] = function*() { yield *['a','b','c'] };
console.log([...1]);

console.log([...new Set([1,1,2,2,3,4])])

console.log(eval('2-2'));
console.log(eval('2_9'));

const x = (() => {
  try {
    return 10;
  } finally {
    return 20;
  }
})();
console.log(x);