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Node.js | dns.resolve4() Method
  • Last Updated : 14 Jan, 2020

The dns.resolve4() method is an inbuilt application programming interface of the dns module which is used to resolve IPv4 address (‘A’ record) for the specified hostname using DNS protocol.

Syntax:

dns.resolve4( hostname, options, 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.
  • options: It is in the form of an object.
    • ttl: It is a Boolean parameter specifies whether the Time-To-Live value (TTL) for each record to be retrieved or not. If set to true, TTL for each record is retrieved (in seconds).
  • callback: It specifies a function to be called after DNS resolution of the hostname.
    • error: It specifies error if generated.
    • address: It is a string or object that signifies the returned IPv4 address(es) for the hostname.

Return Value: This method returns error, address through callback function. These data are passed as parameters to the callback function.

Below examples illustrate the use of dns.resolve4() Method in Node.js:



Example 1:




// Node.js program to demonstrate the   
// dns.resolve4() method
  
// Accessing dns module
const dns = require('dns');
  
// Calling dns.resolve4() method for hostname
// geeksforgeeks.org and display them in
// console as a callback
dns.resolve4('geeksforgeeks.org', (err,
    address) => console.log('address: %j', address));

Output:

address: ["34.218.62.116"]

Example 2:




// Node.js program to demonstrate the   
// dns.resolve4() method
  
// Accessing dns module
const dns = require('dns');
  
// Setting options value for
// dns.resolve4() method
const options = {
    ttl: true,
};
  
// Calling dns.resolve4() method for hostname
// geeksforgeeks.org and displaying them
// in console as a callback
dns.resolve4('geeksforgeeks.org', options, (err,
    address) => console.log('address: %j', address));

Output:

address: [{"address":"34.218.62.116", "ttl":9}]

Note: The above program will compile and run by using the node index.js command.

Reference: https://nodejs.org/api/dns.html#dns_dns_resolve4_hostname_options_callback

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