How domains can be emulated with async_hooks

domains-by-async.js

const hooks = async_hooks.create()

setTimeout(() => { // some async task
  setImmediate(() => { // another one
    throw new Error(); // woops!
  })
}, 1000)

/*
With hooks:

init() trigger: 1, id: 2
before() id: 2
init() trigger: 2, id: 3
after() id: 2
before() id: 3
// uncaught exception. Kills the process
*/

/*
With hooks and uncaught exception handler:

init() trigger: 1, id: 2
before() id: 2 // register uncaught exception handler
init() trigger: 2, id: 3
after() id: 2 // deregister uncaught exception handler
destroy() id: 2 // don't really care about this one
before() id: 3 // register uncaught exception handler
process.on('uncaughtException') // oh, it's by id 3 since that's our last entered state
// it was triggered by id 2 -> 1. let's throw the error at 1!
after() id: 3
destroy() id: 3 // don't really care about this one
*/