docs: function pushSingle(arr, element) {
      var index = arr.sortedIndex(element),
          _ = arr._sortedArray;
  
      // original push and unshift are faster than splice
      if (index === 0) {
          _.unshift.call(arr, element);
      } else if (index === arr.length) {
          _.push.call(arr, element);
      } else {
          _.splice.call(arr, index, 0, element);
      }
  }