function indexOfNaN(array, fromIndex, fromRight) {
	    var length = array.length,
	        index = fromRight ? (fromIndex || length) : ((fromIndex || 0) - 1);

	    while ((fromRight ? index-- : ++index < length)) {
	      var other = array[index];
	      if (other !== other) {
	        return index;
	      }
	    }
	    return -1;
	  }
Gets the index at which the first occurrence of `NaN` is found in `array`.
If `fromRight` is provided elements of `array` are iterated from right to left.

@private
@param {Array} array The array to search.
@param {number} [fromIndex] The index to search from.
@param {boolean} [fromRight] Specify iterating from right to left.
@returns {number} Returns the index of the matched `NaN`, else `-1`.