Simple Promisify Function

promisify.js

// Compact version
const promisify = (fn, ...args) => new Promise((resolve, reject) => 
  fn(...args, (error, result) => error && reject(error) || resolve(result))
)

// Example
// function myAsyncFn(options = Object, callback = Function) {}

// Like Promise
promisify(myAsyncFn, { msg: 'test' }).then(result => console.log(result)) 
promisify(cb => myAsyncFn({ msg: 'test' }, cb)).then(result => console.log(result)) // Same

// Or inside async/await function
async function example() {
 const result = await promisify(cb => myAsyncFn({ msg: 'test' }, cb))
 console.log(result)
}