EU6

var squareOfSum = function(limit)
{
    var s = 0;
    for (var i=1; i<=limit; i++)
    {
        s += i;
    }

    return s*s;
};

var sumOfSquares = function(limit)
{
    var s = 0;
    for (var i=1; i<=limit; i++)
    {
        s += i*i;
    }

    return s;
};

var solveEU6 = function()
{
    var start = performance.now();
    var solution = squareOfSum(100) - sumOfSquares(100);
    var elapsed = performance.now() - start;

    return [solution, elapsed];
};

var res = solveEU6();
document.writeln("Solution is: " + res[0] + ". Took " + res[1] + ". milliseconds.");
document.writeln("<br />");