code: function betterIndexOf(arr, value) {
      if (value != value || value === 0) { // eslint-disable-line eqeqeq
          var i = arr.length;
          while (i-- && !is(arr[i], value)) {
              // eslint-disable-line no-empty
          }
      } else {
          i = [].indexOf.call(arr, value);
      }
      return i;
  }
docs: More reliable indexOf, courtesy of @WebReflection