## Equal Sides Of An Array

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.

**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.

**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: Array index starts at 0 in Javascript

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

**Output format**
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.

#### Solution

```
function findEvenIndex(arr) {
var sum = 0,
leftSum = 0;
// add all ints first
for (var i = 0; i < arr.length; i++) {
sum = sum + arr[i];
}
// subtract all ints so you can find the middle with an exit clause if statement
for (var i = 0; i < arr.length; i++) {
sum = sum - arr[i];
if (leftSum === sum) {
return i;
}
leftSum = leftSum + arr[i];
}
return -1;
}
```