Denis Elistratov Lendar

This article has been given a more permanent home on my blog. Also, since it was first written, the development of the Promises/A+ specification has made the original emphasis on Promises/A seem somewhat outdated.

You're Missing the Point of Promises

Promises are a software abstraction that makes working with asynchronous operations much more pleasant. In the most basic definition, your code will move from continuation-passing style:

getTweetsFor("domenic", function (err, results) {
 // the rest of your code goes here.

This is a fork of Bootstrap Typeahead that adds minimal but powerful extensions.

For example, process typeahead list asynchronously and return objects

  # This example does an AJAX lookup and is in CoffeeScript
  $('.typeahead').typeahead(
    # source can be a function
    source: (typeahead, query) ->
 # this function receives the typeahead object and the query string

	Latency Comparison Numbers (~2012)
	----------------------------------
	L1 cache reference 0.5 ns
	Branch mispredict 5 ns
	L2 cache reference 7 ns 14x L1 cache
	Mutex lock/unlock 25 ns
	Main memory reference 100 ns 20x L2 cache, 200x L1 cache
	Compress 1K bytes with Zippy 3,000 ns 3 us
	Send 1K bytes over 1 Gbps network 10,000 ns 10 us
	Read 4K randomly from SSD* 150,000 ns 150 us ~1GB/sec SSD

	# First add a rule for all local traffic to port 80 to go into pipe 1
	# 100 is the rule number which will be used for referencing the rule later
	sudo ipfw add 100 pipe 1 ip from 127.0.0.1 to 127.0.0.1 dst-port http
	# To display the rule use
	# sudo ipfw show 100

	# configure the settings of the pipe as you please
	# 50kbit/s bandwidth
	sudo ipfw pipe 1 config bw 50Kbit
	# 200ms lag

	var parser = document.createElement('a');
	parser.href = "http://example.com:3000/pathname/?search=test#hash";

	parser.protocol; // => "http:"
	parser.hostname; // => "example.com"
	parser.port; // => "3000"
	parser.pathname; // => "/pathname/"
	parser.search; // => "?search=test"
	parser.hash; // => "#hash"
	parser.host; // => "example.com:3000"

	# salt-minion.conf
	description "salt-minion upstart daemon"
	author "Jeff Bauer <[email protected]>"

	# copy this file to /etc/init

	start on (net-device-up and local-filesystems)
	stop on shutdown

	expect fork


	from deployment.cuisine import *
	from fabric.api import *
	from fabric.context_managers import *
	from fabric.utils import puts
	from fabric.colors import red, green

	import simplejson
	import os

	echo 'export PATH=$HOME/local/bin:$PATH' >> ~/.bashrc
	. ~/.bashrc
	mkdir ~/local
	mkdir ~/node-latest-install
	cd ~/node-latest-install
	curl http://nodejs.org/dist/node-latest.tar.gz \| tar xz --strip-components=1
	./configure --prefix=~/local
	make install # ok, fine, this step probably takes more than 30 seconds...
	curl https://www.npmjs.org/install.sh \| sh