CoffeeScript version of angular directive from this blog: http://rogeralsing.com/2013/08/26/angularjs-directive-to-check-that-passwords-match-followup/#comment-4344

Alternate Implementation

directive = ->
  {
    restrict: 'A'
    scope: true
    require: 'ngModel'
    link: (scope, elem, attrs, control) ->
      control.$parsers.unshift (value) ->
        clearTimeout scope.match_password_timeout if scope.match_password_timeout

        if value != ''
          is_valid = -> 
            e1 = value
            e2 = scope[attrs.passwordMatch]
            control.$setValidity 'match', e1 == e2
            scope.$apply()
          scope.match_password_timeout = setTimeout is_valid, 600
        else
          control.$setValidity('match', true)
  }

app.directive 'passwordMatch', [ directive ]

Original

directive = ->
  {
    restrict: 'A'
    scope: true
    require: 'ngModel'
    link: (scope, elem, attrs, control) ->
      checker = ->
        e1 = scope.$eval(attrs.ngModel)      
        e2 = scope.$eval(attrs.passwordMatch)
        e1 == e2
      scope.$watch checker, (n) ->
        control.$setValidity('unique', n)
  }

app.directive 'passwordMatch', [ directive ]