class app.UpdateChecker  constructor: ->    @lastCheck = Date.now()     $.on window, 'focus', @onFocus    app.serviceWorker?.on 'updateready', @onUpdateReady     setTimeout @checkDocs, 0   check: ->    if app.serviceWorker      app.serviceWorker.update()    else      ajax        url: $('script[src*="application"]').getAttribute('src')        dataType: 'application/javascript'        error: (_, xhr) => @onUpdateReady() if xhr.status is 404    return   onUpdateReady: ->    new app.views.Notif 'UpdateReady', autoHide: null    return   checkDocs: =>    unless app.settings.get('manualUpdate')      app.docs.updateInBackground()    else      app.docs.checkForUpdates (i) => @onDocsUpdateReady() if i > 0    return   onDocsUpdateReady: ->    new app.views.Notif 'UpdateDocs', autoHide: null    return   onFocus: =>    if Date.now() - @lastCheck > 21600e3      @lastCheck = Date.now()      @check()    return