Promises in Node.js 8.x Core

after-promisify.js

const promisify = require('util').promisify;
const fs = require('fs');
const stat = promisify(fs.stat);
const writeFile = promisify(fs.writeFile);
const appendFile = promisify(fs.appendFile);

async function exists(f) {
    try {
        const stats = await stat(f);
        return true;
    } catch (e) {
        return false;
    }
}

async function main() {
    const filename = './example.txt';
    const timestamp = new Date().toISOString();
    const fileExists = await exists(filename);

    if (fileExists) {
        try {
            await appendFile(filename, `Updated file on ${timestamp}\n`);
            console.log('Successfully updated file');
        } catch(e) {
            console.err('Failed to update file');
        }
    } else {
        try {
            await writeFile(filename, `Created file on ${timestamp}\n`);
            console.log('Successfully created file');
        } catch (e) {
            console.err('Failed to create file');
        }
    }
}

main();