CODEWITHSUNDEEP
node.jsrecursionpromise
JSX
JSX

Reputation: 85

Promise not working inside recursion function

function checkFileName(n = 0) {
    return new Promise((resolve, reject) => {
        fs.open("./npm"+n+".txt", 'r', function(err, res) {
            if (err) {
                resolve("./npm"+n+".txt")
            } else {
                n++
                checkFileName(n)
            }
        })
    })
}
checkFileName().then(Name => {
    console.log(Name)
})

but it's not resolve anything where's the wrong ?

Upvotes: 0

Views: 147

Answers (2)

Praveen Tamil
Praveen Tamil

Reputation: 1156

Please change checkFileName(n) to checkFileName(n).then(resolve)

One of the solutions would be as follows:

function checkFileName(n = 0) {
    return new Promise((resolve) => {
        const filePath = "./npm"+n+".txt";
        fs.open(filePath, 'r', function(err, res) {
            if (err) {
                resolve(filePath)
            } else {
               checkFileName(n+1).then(resolve)
            }
        })
    })
}
checkFileName().then(Name => {
    console.log(Name)
})

Upvotes: 0

Ernesto
Ernesto

Reputation: 4272

Any specific reason you is doing it like that ?


// Node.js program to demonstrate the 
// fs.readdir() method 

  
// Import the filesystem module 

const fs = require('fs'); 

const path = require('path'); 

  
// Function to get current filenames 
// in directory with specific extension 
fs.readdir(__dirname, (err, files) => { 

  if (err) 

    console.log(err); 

  else { 

    console.log("\Filenames with the .txt extension:"); 

    files.forEach(file => { 

      if (path.extname(file) == ".txt") 

        console.log(file); 

    }) 

  } 
})

Instead of reading a file at the time, you can read the hole dir and iterate over them returned files

Upvotes: 1

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