gistfile1.txt

function reduce(arr, fn, initial) {
        return (function reduceOne(index, value) {
          if (index > arr.length - 1) return value // end condition
          return reduceOne(index + 1, fn(value, arr[index], index, arr)) // calculate & pass values to next step
        })(0, initial) // IIFE. kick off recursion with initial values
      }
    
      module.exports = reduce