Asynchronously read and write files in Node.js.

package.json

{
  "name": "read_write",
  "version": "1.0.0",
  "description": "Asynchronously read and write files.",
  "private": true,
  "main": "read_write.js",
  "type": "module",
  "scripts": {
    "start": "node read_write.js",
    "test": "echo \"Error: no test specified\" && exit 1"
  },
  "author": "Kieran Barker <kieran@barker.codes> (https://barker.codes/)",
  "license": "MIT"
}

read_write.js

import * as fs from 'fs';
import * as fsPromises from 'fs/promises';

//
// Read
//

// Callback API

fs.readFile('./package.json', 'utf8', (error, data) => {
  if (error) {
    throw error;
  } else {
    console.log(data);
  }
});

// Promises API

// fsPromises
//   .readFile('./package.json', 'utf8')
//   .then(console.log)
//   .catch(console.error);


//
// Write
//

const file = 'hello_world.txt';
const data = 'Hello, World!';

// Callback API

fs.writeFile(file, data, 'utf8', error => {
  if (error) {
    throw error;
  } else {
    console.log(`Successfully wrote '${data}' to ${file}.`);
  }
});

// Promises API

// fsPromises
//   .writeFile(file, data, 'utf8')
//   .then(() => console.log(`Successfully wrote '${data}' to ${file}.`))
//   .catch(console.error);

Read the blog post.