异步/等待嵌套问题？代码块未执行

Question

我有一段代码似乎没有执行。我在 Ubuntu 16.04

上使用 Node.Js 8.9

const puppet =  require("puppeteer");
const fs = require("fs");

let oldIP = "";
( async () =>{
const browser = await puppet.launch({headless:false});
const Page = await browser.newPage();

try {
await Page.goto("http://192.168.100.1");
await Page.waitFor(1000);

await Page.click("#txt_Username");
await Page.keyboard.type(username);
await(console.log("Entered Username"));

await Page.focus("#txt_Password");
await Page.keyboard.type(passwd);
await(console.log("Entered Password"));

await Page.click("#button");
await(console.log("Authenticating"));
await Page.waitForNavigation("load");
await Page.goto("http://192.168.100.1/html/bbsp/waninfo/waninfo.asp");



let ip = await Page.evaluate(async ()=>{
let address = await document.querySelector("#record_0>td:nth-child(3)").innerText;
await console.log(address);
return address;
});

await console.log("Public(NEW) IP Address is: "+ ip);    

fs.readFileSync("Currentaddress.txt", "utf8", async (err,data)=>{
    if(err) {
        console.log(err);
    }
    console.log("Test:"+oldIP);

    //Why is this code not getting executed?
    if(data){
        oldIP = data.trim();
        await console.log("Old IP is :"+oldIP);
    }


});

await (async ()=>{
    if (ip!==oldIP){
        fs.writeFileSync("Currentaddress.txt", ip, "utf8", async (err,data)=>{
            if(err) console.log(err);   
        });

    await console.log("Old IP 2 is :"+oldIP);   
    await console.log("new Ip written  "+ip);
    await process.exit(1);
    }
    //If they're the same
    await (async ()=>{
    await console.log("No changes Noted");
    await process.exit(1);
    })();

})();

}
//end of try block

catch(error){
    console.log(error);
}
})();

let username = "root";
let passwd = "process.env.PASSWD";

注释 //why is this code not getting executed? 下的代码块未触发。我添加了 console.log() 来检查它并没有触发。代码运行时没有任何语法错误。

我正在尝试创建一个脚本来检查我的路由器的 public IP 地址。我已成功获取IP并将其写入txt文件。

但是，读取文件似乎不起作用。

这是我的输出，

Entered Username
Entered Password
Authenticating
Public(NEW) IP Address is: xx.xx.xxx.xx
Old IP 2 is :
new Ip written  xx.xx.xxx.xx

为了安全起见，我已经混淆了 IP，但它 return 是一个有效的 IP 地址。

Old IP 2 is : 然而仍然是空白。

我错过了什么？

Answer 1

函数 fs.readFileSync 是同步的，所以试试这个：

try {
  var data = fs.readFileSync("Currentaddress.txt"), {encoding: "utf8"});
  if(data){
    var oldIP = data.trim();
    console.log("Old IP is :"+oldIP);
  }
} catch (error) {
    console.log(err);
}

Answer 2

readFileSync 是同步的。如果你想要异步功能，你应该使用 fs.readFile https://nodejs.org/api/fs.html#fs_fs_readfile_path_options_callback

其实应该是这样的：

fs.readFile("Currentaddress.txt", "utf8", (err,data)=>{
    if(err) {
        console.log(err);
    }
    console.log("Test:"+oldIP);

    //Why is this code not getting executed?
    if(data){
        oldIP = data.trim();
        console.log("Old IP is :"+oldIP);
    }


});

如果你想等待fs.readFile你应该先承诺它。

Answer 3

而不是使 readFileSync 将 readFile 转换为 promise 并使用 await 调用。因为如果您使用 readFileSync，它会阻塞线程并停止其他进程，直到 readFileSync 完成。

使用 util.promisify.

将 readFile 回调转换为 promise

const fs = require("fs");
const util = require('util');
const readFile = util.promisify(fs.readFile);

使用等待

let data = await readFile('Currentaddress.txt', 'utf8');
if (data) {
    oldIP = data.trim();
    await console.log("Old IP is :" + oldIP);
}

异步/等待嵌套问题？代码块未执行

Async/ Await nesting issues ? Block of code not executing

logic

node.js

async-await

puppeteer