How do I return a result in a file finding function (Node.js)?

Question

Using Node.js, I'm trying to search in the current directory for a specific file with a random number appended at the end of the filename. After some searching online I found this package would probably be best for the job, but I can't seem to make it work.

This is what I have so far:

const find = require('find');

function func1() {
    const x = find.file(/solution[0-9]*\.json/, __dirname, function(files) {
        console.log(files[0]);
        return files[0];
    });
    console.log(x);
}

func1();

This does a great job at finding the correct file and printing it to the console, but I still can't use the path to that file in func1, which is what I needed. This is the result I get:

{ error: [Function: error] }
C:\Users\dir1\dir2\solution78029853.json

I've tried multiple 'experimental' possible syntaxes but none of it seems to work and this is really the closest I can get. I did notice that the { error: [Function: error] } is displayed before the console.log(files[0]);, but I'm not really sure if that's the problem and if it is, I don't know how I can prevent it. Without the const x = and the console.log(x); I get no error, and only the path is displayed, so I'm sure something with that is wrong; I just don't know what. I've been searching the web for over an hour now with no progress so hopefully someone knows what (probably simple) thing I've been doing wrong.

Edit of func1() after Bergur's comment:

function func1() {
    const x = find.file(/solution[0-9]*\.json/, __dirname, function(files) {
        console.log(files[0]);
        return files[0];
    })
    .error(function(err) {
        if (err) {
            //
        }
    });
    console.log(x);
}

This doesn't produce the error, but just prints undefined instead for console.log(x);.

Have you tried to use .error to see what error you are getting?: getting:https://www.npmjs.com/package/find#errorcallback — Bergur, Nov 13 '19 at 23:21
I'm very much a newbie at JavaScript, which doesn't really help. I wasn't sure how to do this so I edited the question with the way I added it to my code... — Hedde, Nov 13 '19 at 23:46
no problem, we all had to start somewhere. Just console.log(err) inside that and hopefully it should show you something. — Bergur, Nov 14 '19 at 00:16
I believe you're running into this classic: https://stackoverflow.com/questions/14220321/how-do-i-return-the-response-from-an-asynchronous-call — Khauri, Nov 14 '19 at 00:47

score 0 · Answer 1 · answered Nov 13 '19 at 23:13

0

console.log(x) is not inside the func1() function

If you want to check the value of x, add a return statement inside the func1 function then console.log(func1())

answered Nov 13 '19 at 23:13

PJ Concepcion

108
1
13

Thank you for pointing that out, I edited the question so it now correctly represents the code I have so far. In the actual code however, `console.log(x)` is inside the `func1()` function so this should also work to check the value of x... (right?) – Hedde Nov 13 '19 at 23:19

Grisho4ek · Answer 2 · 2019-11-15T18:35:28.080

0

This works 100%

//Try this
const util = require('util'); //https://nodejs.org/api/util.html
const findFileAsync = util.promisify(find.file);
const func1 = async () => {
  try{
    const results = await findFileAsync(/solution[0-9]*\.json/, __dirname);
    console.log(results[0]);
  } catch(err){
    console.log(err);
  }
}
func1();

edited Nov 15 '19 at 18:35

answered Nov 14 '19 at 00:45

Grisho4ek

1
1

I went with the other answer since that was more similar to the code I already had, but thank you for taking the time to answer! – Hedde Nov 14 '19 at 12:13
Don’t forget to use try/catch block in async functions. – Grisho4ek Nov 15 '19 at 18:34

score 0 · Accepted Answer · answered Nov 14 '19 at 01:56

The function find.file is asynchronous meaning that you will get the results in a callback (third argument of that function). Assuming you are using ES6 and want to avoid the callback hell problem, you could use async and await like this:

const find = require('find');

async function findFile(name, path) {
  return new Promise(function (ok, fail) {
    find.file(name, path, function(files) {
        ok(files.find(_ => true)) // resolve promise and return the first element
    });
  });
}

async function func1() {
    const x = await findFile(/testFile[0-9]/, "files")
    console.log(`Path to my file: ${x}`);
}

func1();

Link: https://repl.it/repls/ZestyJauntyApplicationserver

How do I return a result in a file finding function (Node.js)?

3 Answers3