setImmediate vs setTimeout vs process.nextTick

[Kikobeats]

   ┌───────────────────────┐
┌─>│        timers         │
│  └──────────┬────────────┘
│  ┌──────────┴────────────┐
│  │     I/O callbacks     │
│  └──────────┬────────────┘
│  ┌──────────┴────────────┐
│  │     idle, prepare     │
│  └──────────┬────────────┘      ┌───────────────┐
│  ┌──────────┴────────────┐      │   incoming:   │
│  │         poll          │<─────┤  connections, │
│  └──────────┬────────────┘      │   data, etc.  │
│  ┌──────────┴────────────┐      └───────────────┘
│  │        check          │
│  └──────────┬────────────┘
│  ┌──────────┴────────────┐
└──┤    close callbacks    │
   └───────────────────────┘

• Use setImmediate if you want to queue the function behind whatever I/O event callbacks that are already in the event queue.

• Use process.nextTick to effectively queue the function at the head of the event queue so that it executes immediately after the current function completes. It's slightly faster than setTimeout:

'use strict'

var bench = require('fastbench')

var run = bench([
  function benchSetImmediate (done) {
    setImmediate(done)
  },
  function benchNextTick (done) {
    process.nextTick(done)
  }
], 1024 * 1024)

// run them two times
run(run)

Considerations on browser side

• on browser side, setImmediate/process.nextTick is not available.
• A simple solution is setTimeout(fn, 0).

[Kikobeats]

Related: https://github.com/jamiebuilds/tickedoff