I would like to know in my typescript file (spfx) if i am currently running gulp serve or gulp build.

for example in C# there is something like

#if DEBUG
  // debug stuff goes here
#else
  // release stuff goes here
#endif

How do i achieve something similar for my gulp/spfx/TS, meaning while in TS inside my component, to split my code in case its serve or build?

As far as researched i saw you can make all kinds of enviorment variables for NODE but not for the typescript files.