Node.js setImmediate, setTimeout, how do they work?

Question

Node.js

function timeout0() {
console.log('timeout 0');
}
function immediate() {
console.log('immediate');
}
setTimeout(timeout0, 0);
setImmediate(immediate);
If you run this code 10 times, you can see that the order of the functions is different, sometimes timeout 0 fires first, and sometimes immediate. Why is that?

Answer 1

Reading the doc :
Those. these are optimization lags, most likely

Answer 2

https://nodejs.org/en/docs/guides/event-loop-timer...