docs: function indexOf(element, fromIndex) {
      /* jshint validthis:true */
      var arr = toArray(this),
          index;
  
      if (fromIndex) {
          arr = arr.slice(fromIndex);
      }
  
      index = binarySearch(arr, element, this.comparator);
  
      if (index < 0) {
          return -1;
      } else {
          return index;
      }
  }