How to get event when system is about to go to sleep

Question

Is it possible to get notified when the system is about to change its power state to sleep?

Something like

process.on('sleep', () => foo())

When going to sleep, the process does not get killed or exit, so answers from doing a cleanup action just before node.js exits do not suffer.

Answer 1

Your programm receive informations from your Operating System in linux from signals. I guess the signal you are looking for is from the following list:

---

To handle signals in node.js here is how you do it :

// Begin reading from stdin so the process does not exit.
process.stdin.resume();

process.on('SIGINT', () => {
  console.log('Received SIGINT. Press Control-D to exit.');
});

// Using a single function to handle multiple signals
function handle(signal) {
  console.log(`Received ${signal}`);
}

process.on('SIGINT', handle);
process.on('SIGTERM', handle);