javascript - Create handler for asynchronous code -

i'm trying create async version of eval , i'm looking method of converting or wrapping async operation doesn't supply it's own callback.

each 1 of these lines runs time-consuming operation doesn't have handler when it's done.

var fs = require('fs') settimeout(function () { throw new error ('hi') }, 3000) settimeout(function () { return 'hi' }, 3000) eval("settimeout(function () { throw new error ('hi') }, 3000)") fs.readfilesync('./package.json', 'utf8') 

i know fs has "async" counterpart fs.readfile, example i'm interested in how i'd convert sync version async.

how craft way of wrapping 1 of these operations?

i got close doing using domain module.

the normal try / catch wont cut because code asyncronous.

try {   settimeout(function () { throw new error ('hi') }, 3000) } catch (e) {   // no error } 

however can use domain catch error, this.

var domain = require('domain') var d = domain.create(); d.on('error', function (e) {   return reject(e) }) d.run(function () {   settimeout(function () { throw new error ('hi') }, 3000) }) 

however there's no way know if function finished running , there no error.

there's talk in node community of deprecating domain , replacing async_wrap can't work either.

i'm looking way convert sync async (synchronous asynchronous). or more async async handler.

both bluebird , async have ways of converting sync code async, not async code async handler.

var _eval = require('eval') var async = require('async') var promise = require('bluebird') var _evalcallback = async.wrapsync(_eval) var _evalpromise = promise.method(_eval)  var code = [   'settimeout(function () {',   '  throw "hello"',   '}, 3000)' ].join('\n')  _evalcallback(code, "hi.js", {}, true, function () {   console.log(arguments) // => { '0': null, '1': {} } })  _evalpromise(code, "hi.js", {}, true)   .then(function () {     console.log(arguments) // => { '0': {} }   })   .catch(function () {     console.log(arguments)   })