reduce_sum.js

// Standard
[1, 2, 3, 4, 5, 6, 7].reduce((total, num) => total + num);

// Reusable functional style
const add = (...nums) => nums.reduce((total, num) => total + num);
add(1, 2, 3, 4, 5, 6, 7);

// Returns: 28