Vimperator ex file defining commands to go back/forward in a duplicated tab (like middle-clicking the navigation buttons)

backt-forwardt.vimperator

" Vimperator ex file: add to .vimperatorrc or source with :source command
" Defines commands to go back/forward in a duplicated tab (equivalent to middle-clicking the navigation buttons)

" Example keybindings: gh and gl (replacing the builtin gh binding):
nnoremap  gh :backt<CR>
nnoremap  gl :forwardt<CR>

command! backt -description "Duplicate tab and go back in the browser history" :js backt();
:js <<EOF
  backt = function() {
      var currT = gBrowser.selectedTab;
      var dupT = gBrowser.duplicateTab(currT);
      var dupTB = gBrowser.getBrowserForTab(dupT);
      var backtListener = function () { 
          gBrowser.goBack(); 
          dupTB.removeEventListener("DOMContentLoaded", backtListener);
      };          
      dupTB.addEventListener("DOMContentLoaded", backtListener);
      gBrowser.selectedTab = dupT;
  }
EOF

command! forwardt -description "Duplicate tab and go forward in the browser history" :js forwardt();
:js <<EOF
  forwardt = function() {
      var currT = gBrowser.selectedTab;
      var dupT = gBrowser.duplicateTab(currT);
      var dupTB = gBrowser.getBrowserForTab(dupT);
      var forwardtListener = function () {
          gBrowser.goForward();
          dupTB.removeEventListener("DOMContentLoaded", forwardtListener);
      };
      dupTB.addEventListener("DOMContentLoaded", forwardtListener);
      gBrowser.selectedTab = dupT;
    }
EOF