node-get-ip-address.js

var os = require('os');

function getLocalIp() {
    var interfaces = os.networkInterfaces(),
        address = '';
    for (var k in interfaces) {
        for (var k2 in interfaces[k]) {
            var intf = interfaces[k][k2];
            if (intf.family == 'IPv4' && !intf.internal) {
                address = intf.address;
            }
        }
    }
    return address;
}