js bitwise cheat sheet

gistfile1.md

js bitwise cheat sheet

var INIT = 0x1      // 0 0 0 0 1
  , PENDING = 0x2   // 0 0 0 1 0
  , DONE = 0x4      // 0 0 1 0 0
  , ERROR = 0x8     // 0 1 0 0 0
  , SUCCESS = 0x10  // 1 0 0 0 0
  , ALL = 0x1f      // 1 1 1 1 1

set

var state = INIT
state &=~ INIT // remove INIT
// state = every `1` bit of state BUT NOT any of INIT
state |= PENDING // add PENDING
// state = every `1` bit of both states
state |= ERROR // add ERROR
state &=~ PENDING // remove PENDING
state |= DONE // add DONE
// state has ERROR & DONE
state ^= ALL // toggle all bytes
// state has INIT, PENDING, SUCCESS

• &=~ ANY_STATE remove state
• &=~ ALL remove all states
• |= ANY_STATE add state

check

if(state & (ERROR | SUCCESS)) {
  console.log("is error or success")
  /* `state` HAS (WHETHER `ERROR` OR `SUCCESS`) */
}
if(state & (DONE & SUCCESS)) {
  console.log("is done and successful")
  /* `state` HAS (`DONE` AND `SUCCESS`) */
}
if(!(state & (DONE | SUCCESS))) {
  console.log("state isn't done or success")
  /* `state` HAS NOT (`DONE` AND `SUCCESS`) */
}
if(state & DONE && !(state & SUCCESS)) {
  console.log("state is done but not success")
  /* `state` HAS `DONE` AND NOT `SUCCESS`) */
}

class

var createState = (function(){

  var hasOwn = {}.hasOwnProperty
    , toString = {}.toString
    , ARRAY_CLASS = "[object Array]"

  function State(states){
    var self = this
      , i = 0, l = states.length
      , a = 1
    for(;i < l; i++) self[states[i]] = (a <<= 1)
    return self
  }

  State.prototype.state = 0

  State.prototype.add = add
  function add(state){
    var self = this
      , ref = 0
      , l
    if(state = [].concat(state)) {
      l = state.length
      for(;l--;) {
        if(!(state[l] in self)) throw "State " + state + " doesn't exist"
        ref |= self[state[l]]
      }
    } 
    self.state |= ref
    return self
  }

  State.prototype.remove = remove
  function remove(state){
    var self = this
      , ref = 0
      , l
    if(state = [].concat(state)) {
      l = state.length
      for(;l--;) {
        if(!(state[l] in self)) throw "State " + state + " doesn't exist"
        ref |= self[state[l]]
      }
    } 
    self.state &= ~ref
    return self
  }

  State.prototype.has = has
  function has(state){
    var self = this
      , ref = 0
      , l
    if(state = [].concat(state)) {
      l = state.length
      for(;l--;) {
        if(!(state[l] in self)) throw "State " + state + " doesn't exist"
        ref |= self[state[l]]
      }
    } 
    return (self.state & ref) == ref
  }

  State.prototype.get = get
  function get(){
    var self = this
      , i
      , state = self.state
      , result = []
    for(i in self) {
      if(!hasOwn.call(self, i) || i == "state") continue
      if(state & self[i]) result.push(i)
    }
    return result
  }

  function s(){}
  s.prototype = State.prototype

  return function(){
    return State.apply(new s, arguments)
  }
})()

usage

var state = createState(["STATE1", "STATE2", "STATE3", "STATE4"])
state.add(["STATE1", "STATE2"])
state.get() // ["STATE1", "STATE2"]
state.add("STATE3").remove("STATE1").get() // ["STATE2", "STATE3"]
state.STATE1 // 2
state.STATE2 // 4
state.STATE3 // 8
state.STATE4 // 16
state.state // 12