JavaScript: Is IP In One Of These Subnets?

The best approach is IMO making use of bitwise operators. For example, 123.123.48.0/22 represents (123<<24)+(123<<16)+(48<<8)+0 (=2071670784; this might be a negative number) as a 32 bit numeric IP address, and -1<<(32-22) = -1024 as a mask. With this, and likewise, your test IP address converted to a number, you can do:

(inputIP & testMask) == testIP

For example, 123.123.49.123 is in that range, as 2071671163 & -1024 is 2071670784

So, here are some tool functions:

function IPnumber(IPaddress) {    var ip = IPaddress.match(/^(\d+)\.(\d+)\.(\d+)\.(\d+)$/);    if(ip) {        return (+ip[1]<<24) + (+ip[2]<<16) + (+ip[3]<<8) + (+ip[4]);    }    // else ... ?    return null;}function IPmask(maskSize) {    return -1<<(32-maskSize)}

test:

(IPnumber('123.123.49.123') & IPmask('22')) == IPnumber('123.123.48.0')

yields true.

In case your mask is in the format '255.255.252.0', then you can use the IPnumber function for the mask, too.

Try this:

var ip2long = function(ip){    var components;    if(components = ip.match(/^(\d{1,3})\.(\d{1,3})\.(\d{1,3})\.(\d{1,3})$/))    {        var iplong = 0;        var power  = 1;        for(var i=4; i>=1; i-=1)        {            iplong += power * parseInt(components[i]);            power  *= 256;        }        return iplong;    }    else return -1;};var inSubNet = function(ip, subnet){       var mask, base_ip, long_ip = ip2long(ip);    if( (mask = subnet.match(/^(.*?)\/(\d{1,2})$/)) && ((base_ip=ip2long(mask[1])) >= 0) )    {        var freedom = Math.pow(2, 32 - parseInt(mask[2]));        return (long_ip > base_ip) && (long_ip < base_ip + freedom - 1);    }    else return false;};

Usage:

inSubNet('192.30.252.63', '192.30.252.0/22') => trueinSubNet('192.31.252.63', '192.30.252.0/22') => false

I managed to solve this by using the node netmask module.You can check if an IP belongs to a subnet by making something like this:

import { Netmask } from 'netmask'const block = new Netmask('123.123.208.0/20')const ip = '123.123.208.0'console.log(block.contains(ip))

Will here print true.

You can install it by using:

npm i --save netmask