const fs = require('fs');

fs.writeFile('test.txt', 'Hello world', (error) => {

if (error) {

console.error(error);

return;

}

console.log('Write complete');

});

// After running above code:

fs.readFile('test.txt', 'utf-8', (error, data) => {

if (error) {

console.error(error);

}

console.log(data);

});

// Read from no file

fs.readFile('nofile.txt', 'utf-8', (error, data) => {

if (error) {

console.error(error);

}

console.log(data);

});

// Readfile promisified

function readFile(file, options) {

return new Promise((resolve, reject) => {

fs.readFile(file, options, (error, data) => {

if (error) {

return reject(error);

}

resolve(data);

})

})

}

// New usage after Node 10

const fsPromises = require('fs').promises;

fsPromises.readFile('test.txt', 'utf-8').then(console.log);

fsPromises.stat('test.txt').then(console.log);