Node.js dns.resolve() Method - GeeksforGeeks

13 Oct, 2021
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 addressAAAA: IPv6 addressANY: Any recordsCNAME: canonical name recordsMX: mail exchange recordsNAPTR: name authority pointer recordsNS: name server recordsPTR: pointer recordsSOA: start of authority recordsSRV: service recordsTXT: text records
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:// Node.js program to demonstrate the   // dns.resolve() method  // Accessing dns moduleconst dns = require('dns');  // Set the rrtype for dns.resolve() methodconst rrtype="A";  // Calling dns.resolve() method for hostname// geeksforgeeks.org and print them in// console as a callbackdns.resolve('geeksforgeeks.org', rrtype, (err, records)         => console.log('records: %j', records));Output:records: ["34.218.62.116"]Example 2:// Node.js program to demonstrate the   // dns.resolve() method  // Accessing dns moduleconst dns = require('dns');  // Set the rrtype for dns.resolve() methodconst rrtype="MX";  // Calling dns.resolve() method for hostname// geeksforgeeks.org and print them in// console as a callbackdns.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:// Node.js program to demonstrate the   // dns.resolve() method  // Accessing dns moduleconst dns = require('dns');  // Set the rrtype for dns.resolve() methodconst rrtype="TXT";  // Calling dns.resolve() method for hostname// geeksforgeeks.org and print them in// console as a callbackdns.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:// Node.js program to demonstrate the   // dns.resolve() method  // Accessing dns moduleconst dns = require('dns');  // Set the rrtype for dns.resolve() methodconst rrtype="NS";  // Calling dns.resolve() method for hostname// geeksforgeeks.org and print them in// console as a callbackdns.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_callbackMy Personal Notes
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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:
// Node.js program to demonstrate the   // dns.resolve() method  // Accessing dns moduleconst dns = require('dns');  // Set the rrtype for dns.resolve() methodconst rrtype="A";  // Calling dns.resolve() method for hostname// geeksforgeeks.org and print them in// console as a callbackdns.resolve('geeksforgeeks.org', rrtype, (err, records)         => console.log('records: %j', records));
Output:
records: ["34.218.62.116"]
Example 2:
// Node.js program to demonstrate the   // dns.resolve() method  // Accessing dns moduleconst dns = require('dns');  // Set the rrtype for dns.resolve() methodconst rrtype="MX";  // Calling dns.resolve() method for hostname// geeksforgeeks.org and print them in// console as a callbackdns.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:
// Node.js program to demonstrate the   // dns.resolve() method  // Accessing dns moduleconst dns = require('dns');  // Set the rrtype for dns.resolve() methodconst rrtype="TXT";  // Calling dns.resolve() method for hostname// geeksforgeeks.org and print them in// console as a callbackdns.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:
// Node.js program to demonstrate the   // dns.resolve() method  // Accessing dns moduleconst dns = require('dns');  // Set the rrtype for dns.resolve() methodconst rrtype="NS";  // Calling dns.resolve() method for hostname// geeksforgeeks.org and print them in// console as a callbackdns.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
Node.js-dns-module
Node.js
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