debounce.coffee

callMethod = (target, method, args) ->
  method = target[method]  if Ember.typeOf(method) is "string"
  method.apply target, args


###
Returns a function, that, when invoked, will only be triggered at most once during a given window of time.
###
Ember.throttle = (target, method, wait) ->
  timeout = undefined
  throttling = undefined
  more = undefined
  result = undefined
  whenDone = undefined
  # detect method signature (adjust for optional arguments)
  if Ember.typeOf(method) is "number"
    wait = method
    method = target
    target = null
  # build timer-reset function
  whenDone = Ember.debounce(->
    more = throttling = false
  , wait)
  # build throttling function wrapper
  return ->
    later = undefined
    args = arguments
    later = ->
      timeout = null
      callMethod target, method, args  if more
      whenDone()

    timeout = setTimeout(later, wait)  unless timeout
    if throttling
      more = true
    else
      result = callMethod(target, method, args)
    whenDone()
    throttling = true
    result


###
Returns a function, that, as long as it continues to be invoked, will not be triggered.
The function will be called after it stops being called for N milliseconds.
If immediate is passed, trigger the function on the leading edge, instead of the trailing.
###
Ember.debounce = (target, method, wait, immediate) ->
  timeout = undefined
  # detect method signature (adjust for optional arguments)
  if Ember.typeOf(method) is "number"
    immediate = wait
    wait = method
    method = target
    target = null
  # build debouncing function wrapper
  return ->
    args = arguments
    later = ->
      timeout = null
      callMethod target, method, args  unless immediate

    callMethod target, method, args  if immediate and not timeout
    clearTimeout timeout
    timeout = setTimeout(later, wait)

###
Returns a function, that, as long as it continues to be invoked, will not be triggered.
The function will be called after it stops being called for N milliseconds.
If immediate is passed, trigger the function on the leading edge, instead of the trailing.
###
Ember.debounce = (target, method, wait, immediate) ->
  timeout = undefined
  # detect method signature (adjust for optional arguments)
  if Ember.typeOf(method) is "number"
    immediate = wait
    wait = method
    method = target
    target = null
  # build debouncing function wrapper
  return ->
    args = arguments
    later = ->
      timeout = null
      callMethod target, method, args  unless immediate

    callMethod target, method, args  if immediate and not timeout
    clearTimeout timeout
    timeout = setTimeout(later, wait)

confirmed to work in Ember 1.0.0-rc.1