Node.js dns.resolve() Method

The

dns.resolve() method

is an inbuilt application programming interface of the dns module which is used to resolve hostname into an array of the resource records.

Syntax:

dns.resolve( hostname, rrtype, callback )

Parameters:

This method accept three parameters as mentioned above and described below:

• hostname: This parameter specifies a string which denotes the hostname to be resolved.
• rrtype: It specifies the resource record type. Its default value is 'A'. The list of records ('A', 'AAAA', 'ANY', 'CNAME', 'MX', 'TXT', 'NS', 'NAPTR', 'PTR', 'SOA', 'SRV') are described below:
  • A: IPv4 address
  • AAAA: IPv6 address
  • ANY: Any records
  • CNAME: canonical name records
  • MX: mail exchange records
  • NAPTR: name authority pointer records
  • NS: name server records
  • PTR: pointer records
  • SOA: start of authority records
  • SRV: service records
  • TXT: text records
• callback: It specifies a function which to be called after DNS resolution of the hostname.
  • error: It specifies error if generated.
  • records: It's string or object that signifies the returned record.
• Return Value:
• This method returns error, records through callback function, These data are passed as parameters to the callback function. Below examples illustrate the use of dns.resolve() Method in Node.js:
• Example 1:
• javascript

  // Node.js program to demonstrate the   
  // dns.resolve() method
  
  // Accessing dns module
  const dns = require('dns');
  
  // Set the rrtype for dns.resolve() method
  const rrtype="A";
  
  // Calling dns.resolve() method for hostname
  // geeksforgeeks.org and print them in
  // console as a callback
  dns.resolve('geeksforgeeks.org', rrtype, (err, records)
           => console.log('records: %j', records));
  

• Output:

• records: ["8.8.8.8"]

• Example 2:
• javascript

  // Node.js program to demonstrate the   
  // dns.resolve() method
  
  // Accessing dns module
  const dns = require('dns');
  
  // Set the rrtype for dns.resolve() method
  const rrtype="MX";
  
  // Calling dns.resolve() method for hostname
  // geeksforgeeks.org and print them in
  // console as a callback
  dns.resolve('geeksforgeeks.org', rrtype, (err, records)
               => console.log('records: %j', records));
  

• Output:

• records: [
      {"exchange":"alt1.aspmx.l.google.com", "priority":5},
      {"exchange":"alt2.aspmx.l.google.com", "priority":5},
      {"exchange":"aspmx.l.google.com", "priority":1},
      {"exchange":"alt3.aspmx.l.google.com", "priority":10},
      {"exchange":"alt4.aspmx.l.google.com", "priority":10}
  ]
  

• Example 3:
• javascript

  // Node.js program to demonstrate the   
  // dns.resolve() method
  
  // Accessing dns module
  const dns = require('dns');
  
  // Set the rrtype for dns.resolve() method
  const rrtype="TXT";
  
  // Calling dns.resolve() method for hostname
  // geeksforgeeks.org and print them in
  // console as a callback
  dns.resolve('geeksforgeeks.org', rrtype, (err, 
      records) => console.log('records: %j', records));
  

• Output:

• records: [
      ["v=spf1 include:amazonses.com include:_spf.google.com -all"],
      ["fob1m1abcdp777bf2ncvnjm08n"]
  ]
  

• Example 4:
• javascript

  // Node.js program to demonstrate the   
  // dns.resolve() method
  
  // Accessing dns module
  const dns = require('dns');
  
  // Set the rrtype for dns.resolve() method
  const rrtype="NS";
  
  // Calling dns.resolve() method for hostname
  // geeksforgeeks.org and print them in
  // console as a callback
  dns.resolve('geeksforgeeks.org', rrtype, (err, 
      records) => console.log('records: %j', records));
  

• Output:

• records: [
      "ns-1520.awsdns-62.org", 
      "ns-1569.awsdns-04.co.uk",
      "ns-245.awsdns-30.com",
      "ns-869.awsdns-44.net"
  ]
  

• Note:
• The above program will compile and run by using the
• node index.js
• command.
• Reference:
• https://nodejs.org/api/dns.html#dns_dns_resolve_hostname_rrtype_callback