(function () {

      var t

      var hiddenProperty = 'hidden' in document ? 'hidden' :

        'webkitHidden' in document ? 'webkitHidden' :

        'mozHidden' in document ? 'mozHidden' :

        null;

      var visibilityChangeEvent = hiddenProperty.replace(/hidden/i, 'visibilitychange');

      var onVisibilityChange = function () {

        document.title = ''

        if (!document[hiddenProperty]) {

          var arr = '喜欢这个效果就收藏吧'

          console.log(arr.length)

          var index = 0

          t = setInterval(() => {

            if (index > arr.length) {

              index = 0;

              document.title = ' '

            }

            var oldTitle = index === 0 ? '' : document.title.slice(0, document.title.length - 1)

            document.title = oldTitle + arr.slice(index, index + 1) + '_'

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          }, 300);

        } else {

          console.log(t)

          if (t) {

            console.log('clear')

            clearInterval(t)

          }

          document.title = '快看，又出bug了'

        }

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