let a = 'world', b = 'hello'
 [a, b] = [b, a]
 console.log(a) // -> hello
 console.log(b) // -> world
// Yes, it's magic




// Find max value
const max = (arr) => Math.max(...arr);
max([123, 321, 32]) // outputs: 321
// Sum array
const sum = (arr) => arr.reduce((a, b) => (a + b), 0)
sum([1, 2, 3, 4]) // output: 10