Node.js dns.resolve4()方法
原文:https://www.geeksforgeeks.org/node-js-dns-resolve4-method/
dns.resolve4()方法是 dns 模块的内置应用程序编程接口，用于使用 dns 协议解析指定主机名的 IPv4 地址(“A”记录)。
语法:
dns.resolve4( hostname, options, callback )
参数:该方法接受三个参数，如上所述，如下所述:
- Hostname: This parameter specifies a string that represents the hostname to be resolved.
- Option: It is the form of an object.
- ttl: It is a Boolean parameter that specifies whether to retrieve the time-to-live value (TTL) of each record. If set to true, TTL (in seconds) of each record will be retrieved.
- Callback: Specify the function to be called after DNS resolution of the host name.
- Error: The specified generation error.
- Address: is a string or object that represents the IPv4 address of the returned host name.
返回值:该方法通过回调函数返回错误、地址。这些数据作为参数传递给回调函数。
以下示例说明了在 Node.js 中 dns.resolve4()方法的使用:
例 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));
输出:
address: ["34.218.62.116"]
例 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));
输出:
address: [{"address":"34.218.62.116", "ttl":9}]
注意:以上程序使用node index.js命令编译运行。
参考:https://nodejs . org/API/DNS . html # DNS _ DNS _ resolve 4 _ hostname _ options _ callback
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