fs.writeFile in a promise, asynchronous-synchronous stuff

Question

I need some help with my code. I\'m new at Node.js and have a lot of trouble with it.

What I\'m trying to do:

1) Fetch a .txt with Amazon products (ASINs) ;<

Answer 1

Use fs.writeFileSync inside the try/catch block as below.

`var fs = require('fs');
 try {
     const file = fs.writeFileSync(ASIN + '.json', JSON.stringify(results))
     console.log("JSON saved");
     return results;
 } catch (error) {
   console.log(err);
  }`

Answer 2

Update Sept 2017: fs-promise has been deprecated in favour of fs-extra.

---

I haven't used it, but you could look into fs-promise. It's a node module that:

Proxies all async fs methods exposing them as Promises/A+ compatible promises (when, Q, etc). Passes all sync methods through as values.

Answer 3

What worked for me was fs.promises.

Example One:

const fs = require("fs")

fs.promises
  .writeFile(__dirname + '/test.json', "data", { encoding: 'utf8' })
  .then(() => {
    // Do whatever you want to do.
    console.log('Done');
  });

Example Two. Using Async-Await:

const fs = require("fs")

async function writeToFile() {
  await fs.promises.writeFile(__dirname + '/test-22.json', "data", {
    encoding: 'utf8'
  });

  console.log("done")
}

writeToFile()

Answer 4

say

const util = require('util')
const fs_writeFile = util.promisify(fs.writeFile)

https://nodejs.org/api/util.html#util_util_promisify_original

this is less prone to bugs than the top-voted answer

Answer 5

If you want to import the promise based version of fs as an ES module you can do:

import { promises as fs } from 'fs'

await fs.writeFile(...)

---

As soon as node v14 is released (see this PR), you can also use

import { writeFile } from 'fs/promises'

Answer 6

Finally, the latest node.js release v10.3.0 has natively supported fs promises.

const fsPromises = require('fs').promises; // or require('fs/promises') in v10.0.0
fsPromises.writeFile(ASIN + '.json', JSON.stringify(results))
  .then(() => {
    console.log('JSON saved');
  })
  .catch(er => {
    console.log(er);
  });

You can check the official documentation for more details. https://nodejs.org/api/fs.html#fs_fs_promises_api