// You are going to be given an array of integers. Your job is to take that array and find an index N where the sum of the integers to the left of N is equal to the sum of the integers to the right of N. If there is no index that would make this happen, return -1.

// For example:

// Let's say you are given the array {1,2,3,4,3,2,1}:
// Your function will return the index 3, because at the 3rd position of the array, the sum of left side of the index ({1,2,3}) and the sum of the right side of the index ({3,2,1}) both equal 6.

// Let's look at another one.
// You are given the array {1,100,50,-51,1,1}:
// Your function will return the index 1, because at the 1st position of the array, the sum of left side of the index ({1}) and the sum of the right side of the index ({50,-51,1,1}) both equal 1.

// Last one:
// You are given the array {20,10,-80,10,10,15,35}
// At index 0 the left side is {}
// The right side is {10,-80,10,10,15,35}
// They both are equal to 0 when added. (Empty arrays are equal to 0 in this problem)
// Index 0 is the place where the left side and right side are equal.

// Note: Please remember that in most programming/scripting languages the index of an array starts at 0.

// Input:
// An integer array of length 0 < arr < 1000. The numbers in the array can be any integer positive or negative.

// Output:
// The lowest index N where the side to the left of N is equal to the side to the right of N. If you do not find an index that fits these rules, then you will return -1.

// Note:
// If you are given an array with multiple answers, return the lowest correct index.
// An empty array should be treated like a 0 in this problem.

/*
come up with a summing function

start loop from i = 1, and end at i = length -2.
  every loop,
    LHS, you slice it
    RHS, you slice it,
    compare sum(LHS) === sum(RHS);
      if equal, return the i;
      else, keep moving through the loop.
  you looped through the whole thing, and didn't return anything?
    then there wasn't anything good.
      return -1;

*/

function sum(arr) {
  return arr.reduce(function(a, b) {
    return a + b;
  });
}

function findEvenIndex(arr) {
  var LHS = [];
  var RHS = [];
  for (var i = 1; i < arr.length - 2; i++) {
    LHS = arr.slice(0, i);
    RHS = arr.slice(i + 1);
    if (sum(LHS) === sum(RHS)) {
      return i;
    }
  }
  return -1;
}

// Test.describe("FindEvenIndex", function() {
//   Test.it("Tests", function() {
//     Test.assertEquals(findEvenIndex([1,2,3,4,3,2,1]),3, "The array was: [1,2,3,4,3,2,1] \n");
//     Test.assertEquals(findEvenIndex([1,100,50,-51,1,1]),1, "The array was: [1,100,50,-51,1,1] \n");
//     Test.assertEquals(findEvenIndex([1,2,3,4,5,6]),-1, "The array was: [1,2,3,4,5,6] \n");
//     Test.assertEquals(findEvenIndex([20,10,30,10,10,15,35]),3, "The array was: [20,10,30,10,10,15,35] \n");
//   });
// });

console.log(findEvenIndex([1,2,3,4,3,2,1]));
findEvenIndex([1, 100, 50, -51, 1, 1]);
findEvenIndex([1,2,3,4,5,6]);
findEvenIndex([20,10,30,10,10,15,35]);