odin-javascript-exercises/calculator/calculator.js

function add(a, b) {
  return a + b;
}

function subtract(a, b) {
  return a - b;
}

function sum(array) {
  return array.reduce((current, total) => total + current, 0);
}

function multiply(array) {
  return array.reduce((current, total) => total * current, 1);
}

function power(a, b) {
  return Math.pow(a, b);
}

function factorial(n) {
  if (n===0){
    return 1;
}
  return n * factorial (n-1);
}

module.exports = {
  add,
  subtract,
  sum,
  multiply,
  power,
  factorial
};