CODEWITHSUNDEEP
node.jsfor-loopfswritefile
PixelBoii
PixelBoii

Reputation: 21

NodeJS unexpectedly adding undefined in beginning of every FS writeFile

Everytime I run my script, undefined is in the beginning and I have no idea why. I want to convert this file

user:pass
user:pass
user:pass

into

username: user
password: pass
username: user
password: pass
username: user
password: pass

but everytime I run it it ends up being..

undefinedusername: user
password: pass
username: user
password: pass
username: user
password: pass

My NodeJS script is the following: 

var fs = require('fs');

var data = fs.readFileSync('details.txt', 'utf-8');
var updatedText;

data = data.replace(/:/g, '\n');

lines = data.split("\n");

for (line in lines) {
    if (line % 2 == 0) {
        updatedText += `username: ${lines[line]}\n`
    } else if (line % 2 == 1) {
        updatedText += `password: ${lines[line]}\n`
    }
}

fs.writeFile('converted.txt', updatedText, function (err) {
    if (err) throw err;
    console.log('Saved!');
  });

All help is of course appreciated! :)

Upvotes: 0

Views: 309

Answers (1)

Sunil Chaudhary
Sunil Chaudhary

Reputation: 4743

updatedText has value undefined. When you do updatedText += ..., the first time when it runs, it adds undefined to the value

var updatedText = "" will fix the issue

Here is a snippet showing the issue: 

var a;
console.log(a+"text1")
var b = ""
console.log(b+"text2")

Upvotes: 1

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