计算一个数值在总数中的占比

getProportion (num, total) {
    num = parseFloat(num);
    total = parseFloat(total);
    if (isNaN(num) || isNaN(total)) {
        return "-";
    }
    return total <= 0 ? "0%" : Math.round((num / total) * 10000) / 100.0 + "%";
}

getProportion(12,3)   // return返回值为：25%