Node.js cannot recognize characters from the serial port
If you use the line parser in Nodejs, it does not remove all line ending characters. I think (though I currently cannot cite it), that only the 'ņ' character is removed from the string. But Serial.println() sends "\r\n" as line ending. That means, that your string is "c\r", which is not equal to "c".

By using the trim() method of the String type, you can remove all white space from start and end of the string, including line ending characters like '\r'.