 
   tick_start: ->
     unless @interval
-      @interval = setInterval(@tick, 1000)
+      @interval = @setInterval(@tick, 1000)
       @setState
         play: true
         is_start: true

@ExerciseBase = React.createClass
  SetIntervalMixin:
    componentWillMount: ->
      @intervals = []

    setInterval: ->
      @intervals.push setInterval.apply(null, arguments)

    componentWillUnmount: ->
      @intervals.map(clearInterval)

  outputSeconds: ->
    @getFormattedTime @state.second


    @setState
      second: @state.second + 1

  mixins: [SetIntervalMixin]

  getInitialState: ->
    @question_count = @props.data.questions.length
