Agfdhyk

Are there some advantages of one of this options?

1.

const fs = require('fs')



const testFunc1 = async () => {

  fs.writeFileSync('text.txt', 'hello world')

}

2.

const fs = require('fs')

const util = require('util')

const writeFilePromisified = util.promisify(fs.writeFile)



const testFunc2 = async () => {

  await writeFilePromisified('text.txt', 'hello world')

}

I am aware the difference betweeen writeFile and writeFileSync. The question is are there some diffs between promisses that return testFunc1 and testFunc2. So ist it the same to calling
testFunc1.then(...) // or await testFunc1
or
testFunc2.then(...) // or await testFunc2

These both promisses will be fullfilled when file writing is done.

fs already contains promisified API that doesn't need promisify.

Asynchronous promise-based version requires to use it as a part of promise-based control flow, while synchronous version doesn't impose this requirement.

Asynchronous readFile/writeFile is non-blocking, while synchronous readFileSync/writeFileSync is blocking but allows to complete a job faster. This may be noticeable during intensive IO operations.

fs.readFile takes a callback function, which means it will not block the execution of your script.
fs.readFileSync however does not take a callback, which means that the execution of your script will be paused untill the process is finished.
Using promisfy is one way to solve this issue, for small files it wont make a difference, but for large files you might want to transform fs.readFileSync into a promise so you wont block the execution.
Hope that helps.

To illustrate the difference between two promises that returns functions:

const fs = require('fs')

const util = require('util')



const testFunc1 = async () => {

  fs.writeFileSync('text.txt', 'hello world')

  console.log('file write done with writeFileSync')

}



const writeFilePromisified = util.promisify(fs.writeFile)



const testFunc2 = async () => {

  await writeFilePromisified('text.txt', 'hello world')

  console.log('file write done with promisified writeFile')

}



console.log('start test1')

testFunc1().then(() => {

  console.log('promise 1 is fullfiled')

})

console.log('start test2')

testFunc2().then(() => {

  console.log('promise 2 is fullfiled')

})

console.log('stop')

Output would be:

start test1

file write done with writeFileSync

start test2

stop

promise 1 is fullfiled

file write done with promisified writeFile

promise 2 is fullfiled

So like estus said testFunc1 blocks the execution of the main thread. testFunc2 do not block.