https://repl.it/Cg3f/0 created by kigold

Cg3f-0.js

function solution(A) {
	var length = A.length;
	if (length == 1){
			return 0;
	}
	if (length < 1){
			return -1;
	}
	if (A.slice(1).reduce((a,b) => a+b) === 0){
		return 0
	}
	if (A.slice(0,length-1).reduce((a,b) => a+b) === 0){
		return length-1
	}
	for (var i=1;i<length-1;i++){
		//left Array
		var sumL = A.slice(0,i).reduce((a,b) => a+b);
		var sumU = A.slice(i+1).reduce((a,b) => a+b);
		if (sumL == sumU) {
			return i;
		}
	}
	return -1;
}

//A = [-1, 3, -4, 5, 1, -6, 2, 1];
A = [1];

console.log("The Answer to this ish is: " + String(solution(A)));

Cg3f-0_console_dump.txt

Native Browser JavaScript
>>> The Answer to this ish is: 0

Need to optimize this