Nodejs Executing Functions

Question

Im new to Nodejs and was wondering why the functions execute out of order instead of how ive written it:

var tor_proxy = require("tor-request")
var s = require("sleep");

tor_proxy.setTorAddress("localhost", 9050);
tor_proxy.TorControlPort.password = "password";

function ShowIP() {
    tor_proxy.request("http://ident.me", function(err, response, body) {
        if(!err && response.statusCode == 200) {
              console.log(body);
        }
    });
}

function Renew() {
    tor_proxy.renewTorSession(function() { console.log("renewed"); });
}


ShowIP();
Renew();
ShowIP();

//Id Like It To Show The IP Then Renew Then Show The New IP
//But Instead It's Out Of Order

Nodejs is event driven (correct me if im wrong) and any help will be appreciated. Thanks :)

That is the expected asynchronous behavior of Node. Take a look at the answer on this post. That should get you started in the right direction. — Narm
– Narm, Commented Nov 20, 2018 at 23:18
@Narm I see, that is a helpful post and I will gave a go to see if I can utilise it — meep
– meep, Commented Nov 20, 2018 at 23:20

Jonathan Tsai · Accepted Answer · 2018-11-21 02:05:09Z

The script will be executed like this:

Inside ShowIP(), tor_proxy.request() sends a request to http://ident.me .
Without waiting for any reply from http://ident.me, function Renew() is executed.
tor_proxy.renewTorSession() is likely to be an asynchronous function. If so, after it begins, the next ShowIP() will be executed without waiting for renewTorSession() to complete.

Depending on how fast http://ident.me replies and how fast renewTorSession() completes, the results may vary.

To execute these functions in proper order, you can search for the following keywords:

Promise
Async/Await
util.promisify() from Node.js
Libraries like Async.js

An example using promise, async and await:

var tor_proxy = require('tor-request');
tor_proxy.setTorAddress('localhost', 9050);
tor_proxy.TorControlPort.password = 'password';

function ShowIP() {
  return new Promise((resolve, reject) => {
    tor_proxy.request('http://ident.me', function (err, response, body) {
      if (err) reject(err);
      else if (response.statusCode !== 200) reject('response.statusCode: ' + response.statusCode);
      else {
        console.log(body);
        resolve();
      }
    });
  });
}

function Renew() {
  return new Promise((resolve, reject) => {
    tor_proxy.renewTorSession(() => {
      console.log('renewed');
      resolve();
    });
  });
}

async function testFunction() {
  // Await makes sure the returned promise completes before proceeding.
  // Note that await keyword can only be used inside async function.
  try {
    await ShowIP();
    await Renew();
    await ShowIP();
    console.log('done!');
  } catch (error) {
    console.log(error);
  }
}

testFunction();

You're a legend! Thanks a lot, I did actually come up with a similar solution using Promises and this looks really good too! Much appreciated.

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