Reading lines or whole buffer from stdin (node.js)

I am developing an interactive console interface in node.js which parses and compiles input. For this purpose I am using readline.question:

require('readline').question('> ', processCommandFunction)

Now the program should also be able to read input piped to stdin from the system shell, i.e.:

$ myprog < myfile.txt

It parses the input, but with readline.question it does so line by line. That breaks some input code which spans over separate lines.

I would like change the behavior of the program so that when used interactively, it processes line by line (like it currently does) but when a file is piped to it, it should process the whole file in one chunk. So I somehow need to check whether more data is coming after a linebreak. Can someone please point me in the right direction?