const arr = [1, 2, 3];
arr[-1] = 10;
console.log(arr.length, arr[-1]);

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

const obj = {};
Object.defineProperty(obj, "prop", {
  value: 42,
  writable: false
});
obj.prop = 100;
console.log(obj.prop);

const arr = [1, 2];
arr.length = 0;
console.log(arr[0]);

const obj = { a: 1 };
Object.seal(obj);
obj.b = 2;
console.log(obj.b);

console.log(0.1 + 0.2 === 0.3);