Codility - Lesson 3: Time Complexity - TapeEquilibrium (https://codility.com/programmers/task/tape_equilibrium/)

tape-equilibrium.js

function solution(A) {
	var sum = A.reduce(function(sum, value) {
		return sum + value
	}, 0)
	var sumLeft = 0
	var min
	for (var i = 1; i < A.length; i++) {
		var value = A[i - 1]
		sumLeft += value
		var diff = Math.abs(2 * sumLeft - sum)
		if (min === undefined) {
			min = diff
		}
		if (diff < min) {
			min = diff
		}
	}
	return min
}

var A = []
A[0] = 3
A[1] = 1
A[2] = 2
A[3] = 4
A[4] = 3

var test = solution(A)
console.log(test, test === 1)