Calculate

Sum

const sum = [1, 2, 3, 4].reduce((acc, curr) => acc + curr, 0);

Max

const max = [5, 2, 8, 1].reduce((acc, curr) => Math.max(acc, curr), -Infinity);

Average

const numbers = [10, 20, 30, 40];
const average = numbers.reduce((acc, curr) => acc + curr, 0) / numbers.length;