The || operator combines conditions where at least one must be true. I'll show you: if (isWeekend || isHoliday) runs when either condition is true, or both. If the left side is true, the right side is never checked.
The entire expression is already true, so checking more conditions would be pointless. You use || for alternatives. Examples: age < 13 || age > 65 for child or senior, key == 'q' || key == 'Q' for quit with any case, error == ERR_TIMEOUT || error == ERR_NETWORK for network problems.