.one(iface, callback) → string
.one(callback)        → string
.one()                → Promise<mac: string>

.all(callback)        → { iface: { type: address } }
.all()                → Promise<Array<{ iface: { type: address } }>>

const macaddress = require('macaddress');

macaddress.one().then(mac => console.log(mac));
// 00:00:00:00:00:00

macaddress.all().then(all => console.log(all));
/*
{
  "en0": {
    "ipv6": "fe80::cae0:ebff:fe14:1da9",
    "ipv4": "192.168.178.20",
    "mac": "ab:42:de:13:ef:37"
  },
  "awdl0": {
    "ipv6": "fe80::58b9:daff:fea9:23a9",
    "mac": "ab:cd:ef:34:12:56"
  }
}
*/