Node: Change in return value of setTimeout

[kefasb]

• 12.19.0:
• all:

What steps will reproduce the bug?

In node:12.19.0-slim docker image setTimeout function returns a value for which isNaN=false
In node:12.18.4-slim docker image setTimeout function returns a value for which isNaN=true

timeoutId = setTimeout(function() {alert("Timeout")}, 1000);
console.log(isNaN(timeoutId))

Is this an intentional behaviour?

[Trott]

Is this an intentional behaviour?

It was indeed an intentional change. https://github.com/nodejs/node/pull/34017

I wonder if perhaps that would have ideally been treated as semver-major, but I can see why that wasn't obvious at the time.

@lundibundi @nodejs/timers

[Fishrock123]

I don't have much to add - the change is definitely something that should have happened at some point. The current maintainers will need figure out what, if anything, to do about this situation.

[kefasb]

Thank you for clarification.

[benjamingr]

@kefasb just to point out - this change should have probably been communicated better and semver-major if people "in the wild" are running into cases where code that checks for node vs. browser timers is starting to fail.

The idea was to make node timers _easier_ to work with and this sort of usage pattern (someone using isNaN to check if the timer they got was a web browser) was missed on our part.

Sorry for breaking your code!