Function to get current timestamp in node
Your code does not work - process.hrtime() does not return with a timestamp of any useful form unless you compare it to another process.hrtime() in the same running program (typically used for measuring performance).

From the documentation: 


  These times are relative to an arbitrary time in the past, and not
  related to the time of day and therefore not subject to clock drift.
  The primary use is for measuring performance between intervals


Bottom line is that the arbitrary time in the past could be anything, and not the same "epoch" as new Date().

There is no way in native JavaScript or Node (without making OS system calls through libraries, etc.) that I know of to get a more granular resolution than the millisecond times from Date.