example.coffee

app.service 'Session', ->
  @create: (@sessionId, @userId) ->
  @destroy: ->
    @id = @userId = null
  @

example.js

app.service('Session', function () {
  this.create = function (sessionId, userId) {
    this.id = sessionId;
    this.userId = userId;
  };
  this.destroy = function () {
    this.id = null;
    this.userId = null;
  };
  return this;
})

example_compiled.js

app.service('Session', function() {
  this.create = function(sessionId, userId) {
    this.sessionId = sessionId;
    this.userId = userId;
  };
  this.destroy = function() {
    return this.id = this.userId = null;
  };
  return this;
});