How to return the result of a function from a nested function?

Question

Node.js

Help please, I'm stupid in the evening. How to do the right one returnin this case? Piece of code:

function readSession (id) {
    var fs = require ("fs"),
        PHPUnserialize = require('php-unserialize');

    fs.readFile("/var/www/cookies/sess_" + id, function (err, boof) {
        if (err) throw err;

        console.log(PHPUnserialize.unserializeSession(boof.toString()));
        return PHPUnserialize.unserializeSession(boof.toString())
    })
}

app.get('/balance.json', function (req, res) {
    res.setHeader("content-type", "application/json; charset=UTF-8");
    res.send(JSON.stringify(readSession(req.cookies.PHPSESSID)));
})

console.logit is displayed normally, but nothing is displayed on the page, because the result is returned readFile, notreadSession

Answer 1

It may be necessary to add a callback to readSession, it will look like this

function readSession (id,callback) {
    var fs = require ("fs"),
        PHPUnserialize = require('php-unserialize');

    fs.readFile("/var/www/cookies/sess_" + id, function (err, boof) {
        if (err) throw err;

        console.log(PHPUnserialize.unserializeSession(boof.toString()));
        callback( PHPUnserialize.unserializeSession(boof.toString()));
    })
}

app.get('/balance.json', function (req, res) {
    res.setHeader("content-type", "application/json; charset=UTF-8");
    readSession(req.cookies.PHPSESSID,function(readSession) {
       res.end(JSON.stringify(readSession));
});
   
})

I think the mistake was that you already sent a response when your function did not have time to read the file.