NodeJs readfilesync returns NAN not file contents

Question

I have written a code for reading a file contents while i running it does not returns file contents but NAN. Below is my code:-

var fs = require('fs');

if (fs.existsSync('Temp')){
console.log('Directory exists, removing...');
if(fs.existsSync('Temp/new.txt')){
    fs.unlinkSync('Temp/new.txt');
}
fs.rmdirSync('Temp');
}

fs.mkdirSync('Temp');

console.log('running');

if(fs.existsSync('Temp')){
process.chdir('Temp');
fs.writeFileSync('test.txt', 'This is some test text for the file2');
fs.renameSync('test.txt', 'new.txt');
console.log('File has size:', + fs.statSync('new.txt').size + ' bytes');
console.log('File contents:', + fs.readFileSync('new.txt', {encoding: 'utf8'}));
}

Marcos Casagrande · Accepted Answer · 2018-04-15T15:28:20.013

You're using the unary operator which converts anything to number instead of concatenating the output.

You either, remove the comma (,) from your console.log and use string concatenation, or remove the + and send the content as console.log second argument.

// I'm concatenating here
console.log('File contents:' + fs.readFileSync('new.txt', {encoding: 'utf8'}));
// I'm sending the content as second argument of console.log
console.log('File contents:', fs.readFileSync('new.txt', {encoding: 'utf8'}));

What you are doing, can be translated to this, which will return NaN unless new.txt content is a number.

console.log(
    'File contents:', 
    Number(fs.readFileSync('new.txt', {encoding: 'utf8'}))
);

console.log('File content: ', + 'new.txt content'); // NaN
console.log('File content: ', Number('new.txt content')); // NaN

console.log('File content: ', 'new.txt content'); // ok
console.log('File content: ' + 'new.txt content'); // ok

Thanks Marcos, this was helpful. I accidently committed the same mistake of using ',' and '+' together which was causing it to return Nan. — Azan Momin, Mar 07 '21 at 13:20

NodeJs readfilesync returns NAN not file contents

1 Answers1