vimperator plugin: browser_object_api.js + tabBlocks

gistfile1.js

liberator.plugins.Block = function () {
  let mTabs = Array.filter(config.tabbrowser.mTabs, function (aNode) aNode.localName == "tab");
  let mCurrentIndex = tabs.index();
  let identify = function (i) {try{return i.linkedBrowser.contentDocument.location.host}catch(e){}};
  let tabBlocks = [], activeBlockIndex, cache;
  mTabs.forEach(function (aTab) {
    let id = identify(aTab);
    if (cache != id && !TreeStyleTabService.getParentTab(aTab)) {
      tabBlocks.push([]);
      cache = id;
    };
    let (index = tabBlocks.length - 1) {
      tabBlocks[index].push(aTab);
      if (!activeBlockIndex && aTab._tPos == mCurrentIndex)
        activeBlockIndex = index;
    };
  });

  let method = {
    get activeBlockIndex ()
      activeBlockIndex,

    activeBlock: function ()
      this.__proto__[this.activeBlockIndex],

    activeBlockTop: function ()
      this.activeBlock()[0],

    activeBlockEnd: function ()
      this.activeBlock().reverse()[0],

    previousBlock: function (i)
      this.__proto__[this.activeBlockIndex - (i || 1)],

    previousBlockTop: function (i)
      this.previousBlock(i)[0],

    previousBlockEnd: function (i)
      this.previousBlock(i).reverse()[0],

    nextBlock: function (i)
      this.__proto__[this.activeBlockIndex + (i || 1)],

    nextBlockTop: function (i)
      this.nextBlock(i)[0],

    nextBlockEnd: function (i)
      this.nextBlock(i).reverse()[0],
  };
  return libly.$U.extend(util.Array(tabBlocks), method);
};

mappings.addUserMap(
  [modes.NORMAL], ["gb^"], "Switch to the this Block first tab.",
  function ()
    let (target = plugins.Block().activeBlockTop())
      target && tabs.select(target._tPos),
  {count: true})

mappings.addUserMap(
  [modes.NORMAL], ["gb$"], "Switch to the this Block last tab.",
  function ()
    let (target = plugins.Block().activeBlockEnd())
      target && tabs.select(target._tPos),
  {count: true})

mappings.addUserMap(
  [modes.NORMAL], ["gbp"], "Switch to the Previous Block first tab.",
  function (count)
    let (target = plugins.Block().previousBlockEnd(count))
      target && tabs.select(target._tPos),
  {count: true})

mappings.addUserMap(
  [modes.NORMAL], ["gbn"], "Switch to the Next Block first tab.",
  function (count)
    let (target = plugins.Block().nextBlockTop(count))
      target && tabs.select(target._tPos),
  {count: true})