JavaScript

const obj = { a: 1, b: 2 };
const proxy = new Proxy(obj, {
  get(target, prop) {
    return prop in target ? target[prop] : 0;
  }
});

console.log(proxy.a, proxy.b, proxy.c);

const array = [1, 2, 3, 4, 5];
const [first, ...rest] = array;

const modified = rest.map((n, i) => i % 2 === 0 ? n * 2 : n);

console.log(first, modified);

const array = [1, 2, [3, 4, [5, 6]]];
const result = array.flat(2).map(n => n * 2);

console.log(result);

const array = [1, 2, [3, 4, [5, 6]]];
const result = array.flat(2).map(n => n * 2);

console.log(result);

function* generator() {
  yield 'a';
  yield* 'bcd';
  yield 'e';
}

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

const array = [1, 2, 3, 4, 5];
const result = array.find(n => n > 3) ? array.every(n => n < 6) : array.some(n => n > 4);

console.log(result);

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

const result = Object.entries(obj2).map(([key, value]) => key + value);

console.log(result);