Await promisified fs.writeFile vs fs.writeFileSync

Question

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.

Answer 1

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

const fsPromises = require("fs/promises");
await fsPromises.writeFile(file, data[, options])

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.

Answer 2

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.