new Vue({
  el: '#app',
  delimiters: ['[[', ']]'],
  data: {
    search: '',
    activeNote: window.location.href.split('#')[1],
    menuShown: true
  },
  methods: {
    seeNote: function (note) {
      this.activeNote = note
      if (window.innerWidth < 768) {
        this.$root.$emit('bv::toggle::collapse', 'index')
      }
    }
  },
  updated: function () {
    var ulElem
    for (var refName in this.$refs) {
      ulElem = this.$refs[refName]
      if (ulElem.getElementsByTagName('a').length === 0) {
        ulElem.style.display = 'none'
        ulElem.previousElementSibling.style.display = 'none'
      } else {
        ulElem.style.display = ''
        ulElem.previousElementSibling.style.display = ''
      }
    }
    // Update URL with new search value
    if (window.history.replaceState) {
      var url = new URL(window.location.href)
      if (this.search) {
        url.searchParams.set('search', this.search)
      } else {
        url.searchParams.delete('search')
      }
      window.history.replaceState({}, null, url.href)
    }
  },
  mounted: function () {
    var self = this
    window.addEventListener('keydown', function (e) {
      var ctrl = e.ctrlKey
      var backspace = e.keyCode === 8
      var slash = e.keyCode === 191
      var letter = e.keyCode >= 65 && e.keyCode <= 90
      if (!ctrl && (backspace || slash || letter)) {
        document.getElementById('search').focus()
      }
    })
    document.getElementById('search').addEventListener('focus', function () {
      if (!self.menuShown) {
        self.$root.$emit('bv::toggle::collapse', 'index')
      }
    })
    self.$root.$on('bv::collapse::state', function (collapseId, isJustShown) {
      self.menuShown = isJustShown
    })

    var url = new URL(window.location.href)
    self.search = url.searchParams.get('search')
  }
})

@@ -364,19 +364,19 @@
 ) %7B%0A    
-var
+let
  ulElem%0A
@@ -384,19 +384,19 @@
    for (
-var
+let
  refName
@@ -807,27 +807,27 @@
 te) %7B%0A      
-var
+let
  url = new U
@@ -1087,19 +1087,19 @@
 ) %7B%0A    
-var
+let
  self = 
@@ -1163,19 +1163,19 @@
 %7B%0A      
-var
+let
  ctrl = 
@@ -1190,19 +1190,19 @@
 y%0A      
-var
+let
  backspa
@@ -1228,19 +1228,19 @@
 8%0A      
-var
+let
  slash =
@@ -1264,19 +1264,19 @@
 1%0A      
-var
+let
  letter 
@@ -1740,11 +1740,11 @@
     
-var
+let
  url

Replace 'var' with 'let'