How to use the dns.lookup function in dns

dnsopts.hints = dns.ADDRCONFIG;
      // The AI_V4MAPPED hint is not supported on FreeBSD, and getaddrinfo
      // returns EAI_BADFLAGS. However, it seems to be supported on most other
      // systems. See
      // http://lists.freebsd.org/pipermail/freebsd-bugs/2008-February/028260.html
      // and
      // https://svnweb.freebsd.org/base/head/lib/libc/net/getaddrinfo.c?r1=172052&r2=175955
      // for more information on the lack of support for FreeBSD.
      if (process.platform !== 'freebsd')
        dnsopts.hints |= dns.V4MAPPED;
    }

    debug('connect: find host ' + host);
    debug('connect: dns options ' + dnsopts);
    self._host = host;
    dns.lookup(host, dnsopts, function(err, ip, addressType) {
      self.emit('lookup', err, ip, addressType);

      // It's possible we were destroyed while looking this up.
      // XXX it would be great if we could cancel the promise returned by
      // the look up.
      if (!self._connecting) return;

      if (err) {
        // net.createConnection() creates a net.Socket object and
        // immediately calls net.Socket.connect() on it (that's us).
        // There are no event listeners registered yet so defer the
        // error event to the next tick.
        process.nextTick(function() {
          self.emit('error', err);
          self._destroy();
        });

dnsopts.hints = dns.ADDRCONFIG;
      // The AI_V4MAPPED hint is not supported on FreeBSD, and getaddrinfo
      // returns EAI_BADFLAGS. However, it seems to be supported on most other
      // systems. See
      // http://lists.freebsd.org/pipermail/freebsd-bugs/2008-February/028260.html
      // and
      // https://svnweb.freebsd.org/base/head/lib/libc/net/getaddrinfo.c?r1=172052&r2=175955
      // for more information on the lack of support for FreeBSD.
      if (process.platform !== 'freebsd')
        dnsopts.hints |= dns.V4MAPPED;
    }

    debug('connect: find host ' + host);
    debug('connect: dns options ' + dnsopts);
    self._host = host;
    dns.lookup(host, dnsopts, function(err, ip, addressType) {
      self.emit('lookup', err, ip, addressType);

      // It's possible we were destroyed while looking this up.
      // XXX it would be great if we could cancel the promise returned by
      // the look up.
      if (!self._connecting) return;

      if (err) {
        // net.createConnection() creates a net.Socket object and
        // immediately calls net.Socket.connect() on it (that's us).
        // There are no event listeners registered yet so defer the
        // error event to the next tick.
        process.nextTick(function() {
          self.emit('error', err);
          self._destroy();
        });

// been solved before in https://github.com/nodejs/node/pull/12342, but was
        // reverted as it had unintended side effects.
        if (Array.isArray(args[0]) && args[0][normalizedArgsSymbol])
            normalized = args[0];
        else
            normalized = normalizeArgs(args);
        let options = normalized[0];
        let cb = normalized[1];
        if (!options.host)
            options.host = '127.0.0.1';

        let family = options.port === undefined ? 0 : native.isIP(options.host);
        if (options.port === undefined || family)
            this._connect(options, family, options.port === undefined ? options.path : options.host, cb);
        else
            dns.lookup(options.host, (err, host, family) => {
                this.emit('lookup', err, options.host, family, host);
                if (err) {
                    this.connecting = false;
                    this._updateRef();

                    this.emit('error', err);
                    return;
                }
                if (this.destroyed) {
                    this.connecting = false;
                    this._updateRef();
                    return;
                }

                this._connect(options, family, host, cb);
            });

var lookup = function(address, family, callback) {
    // implicit 'bind before send' needs to run on the same tick
    var matchedFamily = isIP(address);
    if (matchedFamily)
        return callback(null, address, matchedFamily);

    if (!dns)
        dns = require('dns');

    return dns.lookup(address, family, callback);
};

TEST(function test_lookup_ipv4_explicit(done) {
  var req = dns.lookup('www.google.com', 4, function(err, ip, family) {
    if (err) throw err;
    assert.ok(net.isIPv4(ip));
    assert.strictEqual(family, 4);

    done();
  });

  checkWrap(req);
});

TEST(function test_lookup_localhost_ipv4(done) {
  var req = dns.lookup('localhost', 4, function(err, ip, family) {
    if (err) throw err;
    assert.strictEqual(ip, '127.0.0.1');
    assert.strictEqual(family, 4);

    done();
  });

  checkWrap(req);
});

var dns = require('dns');
  var host = options.host ? options.host : 'localhost';
  var port = Number(options.port);
  var dnsopts = {
    family: (options.family || 4) >>> 0,
    hints: 0,
  };

  if (!util.isNumber(port) || port < 0 || port > 65535)
    throw new RangeError('port should be >= 0 and < 65536: ' + options.port);

  if (dnsopts.family !== 0 && dnsopts.family !== 4 && dnsopts.family !== 6)
    throw new RangeError('family should be 4 or 6: ' + dnsopts.family);

  self._host = host;
  dns.lookup(host, dnsopts, function(err, ip, family) {
    if (self._socketState.destroyed) {
      return;
    }
    self.emit('lookup', err, ip, family);

    if (err) {
      emitError(self, err);
    } else {
      resetSocketTimeout(self);
      process.nextTick(function() {
        connect(self, ip, port);
      });
    }
  });

  return self;

DnsApi.prototype.lookup = function (hostname, family, callback) {
  if (typeof family === 'function') {
    callback = family;
    family = 0;
  }

  dns.lookup(hostname, family, callback);
};