_post-repeat-directive.coffee

#shamelessly copied from
#http://tech.small-improvements.com/2013/09/10/angularjs-performance-with-large-lists/
#https://gist.github.com/rkgarg/7232175
app = require '../../app.coffee'
directiveName = 'postRepeat'
app.directive directiveName, [ '$log',
  ($log) ->
    postRepeat = {}

    scope:
      options: '='

    link: (scope, element, attrs) ->
      attrScope = scope.$parent
      #root parent to all ng-repeats (encapsulating div or whatever)
      parent = attrScope.$parent
      if attrScope.$first
        # lastTime can be updated anywhere if to reset counter at some
        #action if ng-repeat is not getting started from $first
        postRepeat[parent.$id] =
          lastTime: new Date()

        parent.$on '$destroy', ->
          delete postRepeat[parent.$id]
      if scope.options?
        opts = scope.options
        #use init function (via attribute binding (basically options)) to
        # pass the postRepeat object on so the lastTime can be rest
        opts.init(postRepeat[parent.$id],scope) if opts.init? and angular.isFunction opts.init

      if attrScope.$last
        scope.$evalAsync ->
          $log.debug "## DOM rendering list took: " +
            (new Date() - postRepeat[parent.$id].lastTime) + " ms"
          doDelete = if not opts?.doDeleteLastTime? then true else opts?.doDeleteLastTime
          delete postRepeat[parent.$id] if doDelete
]

controller.coffee

app.controller 'Ctrl', ($scope) ->
    _postRepeat = null
    $scope = 
     postRepeatOptions:
      init: (postRepeat, scope) ->
        _postRepeat = postRepeat
      doDeleteLastTime: false    
      
    //some where down the line    ...
    //this is useful for testing infinite scroll where you need to not always erase lastTime untill specific momments
    postRepeat.lastTime =  new Date()    

exampleTemplate.html

<tr ng-repeat="item in items" post-repeat options="postRepeatOptions">…</tr>