function combine(...arrays) {
  return arrays.reduce((acc, arr) => [...acc, ...arr], []);
}

const result = combine([1, 2], [3, 4], [5, 6]);
console.log(result);

const obj = {
  valueOf() {
    return 42;
  }
};

const result = obj + 8;
console.log(result);

function trickyFunction() {
    var a = 10;
    var b = a;
    b = 15;

    const obj1 = { x: 1 };
    const obj2 = obj1;
    obj2.x = 5;

    console.log(a + ' ' + b + ' ' + obj1.x);
}

trickyFunction();