Generator deasync pattern

createAsyncFn.js

/**
 * returns a function that runs an async generator (one which yields async functions), usings auto yield/next thanks to an 'args.next'
 * The created function expects as parameter an optional object with a {cb:callbackFn} property plus aditional custom arguments
 * Can also make a onliner gen runner with it: function runAsyncGen(gen, args) { newAsyncFn(gen)(args) }
 */
function createAsyncFn (gen) {
    return function(args={}, cb) {
        //var cb = (typeof args === 'function') ? args : args.cb
        it = gen(args)    // create iterator from generator, and pass a common object to communicate
        
		args.next = (res)=>{    // pre made callback to pass to async funcions inside generator to keep going on
            let ret = it.next(res)
            if (ret.done && typeof cb === 'function') cb(ret.value) // "return" statement is another "yield" with .done = true
        }

		args.nextIfOK = (err,res)=>{    // to quickly handle (err, res) standard nodejs returns inside a try/catch
			if (!err) args.next(res)
			else it.throw(new Error(err))
		}

        it.next()    // start iterator
    }
}

//  -------------------------------- EXAMPLE 
// Nodejs async readline in a sync fashion
// the 'args' parameter here is the args parameter passed to the funcion, plus a .next function of the current iterator
var promptUser = createAsyncFn( function* (args) {
  var r = require('readline')
  var rl = r.createInterface({input: process.stdin, output: process.stdout })

  // magic here
  var answerA = yield rl.question(`Hello ${args.name}, do you want this? `, args.next)   // or somting like  (err, res)=>args.next({err,res})
  console.log("mmm, let me think about it...")
  yield setTimeout(args.next, 1000)
  var answerB = yield rl.question('are you sure? ', args.next)        
  
  rl.close()    // readline boilerplate
  return {answerA, answerB} // the last 'yield'
})


// now make use of it
promptUser({ name:'Neo', cb:(r)=>{
    console.log('\nAnswers:',r)
}})