Function lookup

lib/dns.js:142–251

(hostname, options, callback)

// Easy DNS A/AAAA look up
// lookup(hostname, [options,] callback)
function lookup(hostname, options, callback) {
  let hints = 0;
  let family = 0;
  let all = false;
  let dnsOrder = getDefaultResultOrder();

  // Parse arguments
  if (hostname) {
    validateStringWithoutNullBytes(hostname, 'hostname');
  }

  if (typeof options === 'function') {
    callback = options;
    family = 0;
  } else if (typeof options === 'number') {
    validateFunction(callback, 'callback');

    validateOneOf(options, 'family', validFamilies);
    // Coerce -0 to +0.
    family = options + 0;
  } else if (options !== undefined && typeof options !== 'object') {
    validateFunction(arguments.length === 2 ? options : callback, 'callback');
    throw new ERR_INVALID_ARG_TYPE('options', ['integer', 'object'], options);
  } else {
    validateFunction(callback, 'callback');

    if (options?.hints != null) {
      validateNumber(options.hints, 'options.hints');
      hints = options.hints >>> 0;
      validateHints(hints);
    }
    if (options?.family != null) {
      switch (options.family) {
        case 'IPv4':
          family = 4;
          break;
        case 'IPv6':
          family = 6;
          break;
        default:
          validateOneOf(options.family, 'options.family', validFamilies);
          // Coerce -0 to +0.
          family = options.family + 0;
          break;
      }
    }
    if (options?.all != null) {
      validateBoolean(options.all, 'options.all');
      all = options.all;
    }
    if (options?.verbatim != null) {
      validateBoolean(options.verbatim, 'options.verbatim');
      dnsOrder = options.verbatim ? 'verbatim' : 'ipv4first';
    }
    if (options?.order != null) {
      validateOneOf(options.order, 'options.order', validDnsOrders);
      dnsOrder = options.order;
    }