JS 根據子網掩碼，網關計算出所有的IP範圍

// 驗證IP的正則
var ip_reg = /^(25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\.(25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\.(25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\.(25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)$/;

// 驗證子網掩碼的正則
var mask_reg = /^(254|252|248|240|224|192|128|0)\.0\.0\.0|255\.(254|252|248|240|224|192|128|0)\.0\.0|255\.255\.(254|252|248|240|224|192|128|0)\.0|255\.255\.255\.(254|252|248|240|224|192|128|0)$/;

// IP轉二進位
function ip_to_binary(ip)
{
    if (ip_reg.test(ip)) {
        var ip_str = "",
            ip_arr = ip.split(".");

        for (var i = 0; i < 4; i++) {
            curr_num = ip_arr[i];
            number_bin = parseInt(curr_num);
            number_bin = number_bin.toString(2);
            count = 8 - number_bin.length;
            for (var j = 0; j < count; j++) {
                number_bin = "0" + number_bin;
            }
            ip_str += number_bin;
        }
        return ip_str;
    }

    return '';
}

// 二進位轉IP
function binary_to_ip(binary)
{
    if (binary.length == 32) {
        a = parseInt(binary.substr(0, 8), 2);
        b = parseInt(binary.substr(8, 8), 2);
        c = parseInt(binary.substr(16, 8), 2);
        d = parseInt(binary.slice(-8), 2);

        return a + '.' + b + '.' + c + '.' + d;
    }

    return '';
}


// 根據子網掩碼和網關計算出IP範圍（網路地址 - 廣播地址）
function get_network_broadcast_addr(mask, ip)
{
    network_broadcast = [];
    network_addr = "";
    
    mask_arr = mask.split(".");
    ip_arr = ip.split(".");
    
    // 計算IP的網路地址 與(&)運算
    for (var i = 0; i < 4; i++) {
        number1 = parseInt(mask_arr[i]);
        number2 = parseInt(ip_arr[i]);
        network_addr += number1 & number2;
        if( i < 3 ){
            network_addr += ".";
        }
    }
    network_broadcast.push(network_addr);

    // 計算廣播地址
    // 子掩碼後面有幾個0，就去掉IP地址後幾位再補1
    mask_binary = ip_to_binary(mask);
    gateway_binary = ip_to_binary(ip);
    
    mask_zero = mask_binary.split(0).length - 1;
    one_number = new Array(mask_zero + 1).join('1'); // IP地址後位補1
    gateway_hou_wei_bu_yi = gateway_binary.slice(0, -mask_zero) + one_number;

    network_broadcast.push(binary_to_ip(gateway_hou_wei_bu_yi));

    return network_broadcast;
}

//  全排列組合演算法（兩兩遞歸組合）
function doExchange(doubleArrays)
{
    var len = doubleArrays.length;
    if(len >= 2){
        var len1 = doubleArrays[0].length;
        var len2 = doubleArrays[1].length;
        var newlen = len1 * len2;
        var temp = new Array(newlen);
        var index = 0;
        for(var i = 0; i < len1; i++){
            for(var j = 0; j < len2; j++){
                temp[index] = doubleArrays[0][i] + '.' + doubleArrays[1][j];
                index++;
            }
        }

        var newArray = new Array(len - 1);
        for(var i = 2; i < len; i++){
            newArray[i - 1] = doubleArrays[i];
        }
        newArray[0] = temp;

        return doExchange(newArray);

    } else{
        return doubleArrays[0];
    }
}

// 返回所有IP
function return_ip(network_addr, broadcast_addr, gateway)
{
    range = [];
    start = network_addr.split(".");
    end = broadcast.split(".");

    // range格式為[[192], [168], [0,1,2...254], [0,1,2...254]]
    for (var i = 0; i < 4; i++) {
        if (start[i] == end[i]) {
            range[i] = [start[i]];
        } else {
            min = Math.min(start[i], end[i]);
            max = Math.max(start[i], end[i]);
            temp = [];
            for (var j = min; j <= max; j++) {
                temp.push(j);
            }
            range[i] = temp;
        }
    }

    ip_list = doExchange(range);
    ip_list.shift(); // 去掉網路地址
    ip_list.pop(); // 去掉廣播地址
    gateway_index = -1;
    
    // 去掉網關
    for (var k = 0; k < ip_list.length; k++) {
        if (ip_list[k] == gateway) {
            gateway_index = k;
            break;
        }
    }
    if (gateway_index > -1) {
        ip_list.splice(gateway_index, 1);
    }

    return ip_list;
}