Promisify a node function

promise_all.js

let filenames = ['index.html', 'blog.html', 'terms.html'];

Promise.all(filenames.map(readFilePromise))
  .then(files => {
    console.log('index:', files[0]);
    console.log('blog:', files[1]);
    console.log('terms:', files[2]);
  })

promise_race.js

function timeout(ms) {
  return new Promise((resolve, reject) => {
    setTimeout(reject, ms);
  })
}

/* Resolves with the first promise fulfilled */
Promise.race([readFilePromise('index.html'), timeout(1000)])
  .then(data => console.log(data))
  .catch(e => console.log("Timed out after 1 second"))

promisify.js

function readFilePromise(filename) {
    return new Promise((resolve, reject) = > {
        fs.readFile(filename, 'utf8', (err, data) = > {
            if (err) reject(err);
            else resolve(data);
        })
    })
}

readFilePromise('index.html')
    .then(data = > console.log(data))
    .catch (e = > console.log(e))