You can stalk your Whatsapp Web main conversation window (1) by copying the content of the file whatsappWebMainWindowStalker.js and (2) pasting it into your browser Javascript console.
Then, you need to run the follow command to become a Whatsapp Web stalker:
mainRun();The status log of the people of your main conversation windows will look like:
!> Felipe Martins - 00:07:21 - offline
Felipe Martins - 00:07:42 - online
Felipe Martins - 00:07:48 - writing...
Felipe Martins - 00:07:50 - online
Felipe Martins - 00:07:52 - offline
When you want to stop stalking, you can run:
mainStop = true;