fs.readFile(A, 'utf-8', function(err, data) {
fs.readFile(B, 'utf-8', function(err, data) {...fs.readFile(C, 'utf-8', function(err, data) {
fs.readFile(D, 'utf-8', function(err, data)...);
function* read() {
yield readFile(A, 'utf-8');
yield readFile(B, 'utf-8');
yield readFile...bluebird = require('bluebird');
const readFile = bluebird.promisify(fs.readFile);
async function read...() {
await readFile(A, 'utf-8');
await readFile(B, 'utf-8');
await readFile(C, 'utf-8');