在继续执行脚本之前，如何等待函数的结果? [英] How to await the result of a function before continuing with the script?

问题描述

我当前正在构建一个Nodejs脚本，该脚本应与Web服务器和本地网络设备进行交互.为了使程序尽可能可靠，我想做一个简单的ping测试，以检查是否可以访问网络设备.

I'm currently building a Nodejs script which should interact with a web server and a local network device. In order to make the program as reliable as possible I want to do a simple ping test to check if the network device can be reached.

var ping = require('ping');

function pingtest(host) {
    ping.sys.probe(host, function (isAlive) {
        var msg = isAlive ? 'host ' + host + ' is alive' : 'host ' + host + ' is dead';
        console.log(msg);

        return isAlive;
    });
}

let pingSuccessful = pingtest('192.168.178.100');

console.log(pingSuccessful);
console.log('Should not executed before pingtest has finished.');

控制台上的输出如下:

undefined
Should not executed before pingtest has finished.
host 192.168.178.100 is dead

问题在于脚本执行应该暂停直到pingtest()完成并返回结果.我的目标是要console.error()一条消息，如果此测试失败，则停止脚本.我已经使用异步等待和其他代码示例在 https://github.com/danielzzz/node上进行了尝试-ping ，但不幸的是，这没有按预期进行.

The problem is that the script execution should pause until pingtest() has finished and returned the result. My goal is to console.error() a message and stop the script if this test failed. I already tried it with async await and the other code examples at https://github.com/danielzzz/node-ping but unfortunately this didn't work as expected.

推荐答案

您根本无法从回调中返回.您可以利用Promise.像这样重构代码:

You simply can not return from a callback. You can make use of Promise. Refactor the code like this:

function pingtest(host) {
  return new Promise((resolve, reject) => {
    ping.sys.probe(host, function (isAlive) {
        var msg = isAlive ? 'host ' + host + ' is alive' : 'host ' + host + ' is dead';
        console.log(msg);

        resolve(isAlive);
    });
  });
}

pingtest('192.168.178.100').then((pingSuccessful) => {
  console.log(pingSuccessful);
});

或者，您必须在ping.sys.probe回调中进行所有操作.

Or, you have to do everything inside ping.sys.probe callback.

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