Entropy

function GetEntropy(text)
{
    var result = 0;
    var stat = Array();
    var sum = 0;
    var i;

    for(i = 0; i < 208; i++)
    {
        stat[i] = 0;
    }

    for(i = 0; i < text.length; i++)
    {
        if((text.charCodeAt(i) >= 0x400 && text.charCodeAt(i) <= 0x44F))
        {
            stat[text.charCodeAt(i) - 0x400]++;
            sum++;
        }

        if((text.charCodeAt(i) >= 0x20 && text.charCodeAt(i) <= 0x7F))
        {
            stat[text.charCodeAt(i) + 0x50 - 0x20]++;
            sum++;
        }
    }

    if(sum > 0)
    {
        for(i = 0; i < 208; i++)
        {
            var prob = stat[i] / sum;
            if(prob > 0)
                result -= (prob * Math.log(prob));
        }
        result /= Math.log(2);
    }

    return result / 8 * 100;
}