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