var nc = require('network-calculator');
console.log(nc('192.168.1.4', '255.255.255.128'));
// >
// {
//   network: '192.168.1.0',
//   bitmask: 25,
//   firsthost: '192.168.1.1',
//   broadcast: '192.168.1.127',
//   lasthost: '192.168.1.126',
//   totalhost: 126
// }