summation.js

/**
 * Write a program that finds the summation of every number from 1 to num. The number will always be a positive integer greater than 0.
 * 
 * For example:
 * summation(2) -> 3
 * 1 + 2
 * 
 * summation(8) -> 36
 * 1 + 2 + 3 + 4 + 5 + 6 + 7 + 8
 */

const summation = (num) => {
    const numArr = Array.from({length: num}).map((i, n) => n + 1),
          sumArr = numArr.reduce((accumulator, currentVal) => accumulator + currentVal, initialVal = 0)
    return sumArr
}

console.log(summation(10))