index.js
function readFile(filename) {
	return new Promise(
		(resolve, reject) => fs.readFile(filename, 'utf8',
			(error, data) => error ? reject(error) : resolve(data)
		)
	);
}
function readFile(filename) {
	return new Promise(
		(resolve, reject) => fs.readFile(filename, 'utf8',
			(error, data) => error ? reject(error) : resolve(data)
		)
	);
}
function readFile ( filename ) { return new Promise ( ( resolve , reject ) => fs . readFile ( filename , 'utf8' , ( error , data ) => error ? reject ( error ) : resolve ( data ) ) ) ; }
Promise fs.readFile
Promise fs . readFile