equilibrium code challenge http://blog.codility.com/2011/03/solutions-for-task-equi.html

equilibrium.js

function equilibrium(numberArray) {
    var lower, higher, equilibriums = [];
    var lowerSum, higherSum;
    
    function sum(arrayParts) {
      return arrayParts.reduce(function (prev, curr) {
            return prev + curr;
        }, 0);
    }
    
    for (var i = 1; i < numberArray.length - 1; i++) {
        lower = numberArray.slice(0, i - 1);
        higher = numberArray.slice(i);
        
        lowerSum = sum(lower);
        higherSum = sum(higher);
      
        if (lowerSum === higherSum) {
            equilibriums.push(i + 1);
        }
    }
    
    if (!equilibriums) {
        return -1;
    } else {
        return equilibriums;
    }
}

equilibrium([-1, 3, -4, 5, 1, -6, 2, 1]);

// Should return [3,5] as 0+1+2 === 4+5+6+7 the same for 5