Write a file in Node.js, creating its path if necessary. Returns a promise.

write-file-promise.js

const fs = require('fs')
const path = require('path')
const mkpath = require('mkpath')

module.exports = function writeFilePromise(fileName, contents) {
	return new Promise((resolve, reject) => {
		mkpath(path.dirname(fileName), err => {
			if (err) reject(err)
			else {
				fs.writeFile(fileName, contents, err => {
					if (err) reject(err)
					else resolve(contents)
				})
			}
		})
	})
}