node . js dnspromses . resolve 4()方法
原文:https://www . geesforgeks . org/node-js-dnspromses-resolve 4-method/
dnsPromises.resolve4()方法是 dns 模块承诺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:
dnsPromises.resolve4( hostname, options )
参数:该方法有两个参数，如上所述，如下所述:
- Hostname: This parameter specifies a string representing 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.
返回值:此方法返回错误，记录。
以下示例说明了在 Node.js 中使用方法:
例 1:
// Node.js program to demonstrate the
// dnsPromises.resolve4() method
// Accessing promises object from dns module
const dns = require('dns');
const dnsPromises = dns.promises;
// Calling dnsPromises.resolve4() method
dnsPromises.resolve4('geeksforgeeks.org').then((res) => {
console.log(res);
});
// Calling dnsPromises.resolve4() method
// asynchronously
(async function() {
// Records from resolve function
const records = await dnsPromises.resolve4(
'geeksforgeeks.org');
// Printing records
console.log("from async: ");
console.log(records);
})();
输出:
[ '34.218.62.116' ]
from async:
[ '34.218.62.116' ]
例 2:
// Node.js program to demonstrate the
// dnsPromises.resolve4() method
// Accessing promises object from dns module
const dns = require('dns');
const dnsPromises = dns.promises;
// Setting options for dnsPromises.resolve4() method
const options = {
ttl:true,
};
// Calling dnsPromises.resolve4() method
// asynchronously
(async function() {
// Records from resolve4 function
const records = await dnsPromises.resolve4(
'geeksforgeeks.org', options);
// Printing records
console.log("from async: ");
console.log(records);
})();
输出:
from async:
[ { address: '34.218.62.116', ttl: 30 } ]
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 _ dnspromses _ resolve 4 _ hostname _ options
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