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));
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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));
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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