Sum All Numbers In a Range

index.js

/*
We'll pass you an array of two numbers. Return the sum of those two numbers and all numbers between them.

The lowest number will not always come first.
*/

function sumAll(arr) {
  var newArray = [];
  var result;

  (function createArray(arr) {
    for (var i = Math.min(...arr); i <= Math.max(...arr); i++) {
      newArray.push(i);
    }
  })(arr), add(newArray);

  function add(newArray) {
    result = newArray.reduce(function(sum, value) {
      return sum + value;
    }, 0);
  }
  return result;
}

//sumAll([1, 4]); //should return 10.
//sumAll([4, 1]); //should return 10.
sumAll([5, 10]); //should return 45.
//sumAll([10, 5]); //should return 45.