
Ask HN: Why don't languages that support Promises include timeouts? - 0x0aff374668
I&#x27;ve been programming with promises for several years now, and I find myself using a common pattern of adding a race timeout promise. It seems like a useful feature, why isn&#x27;t it implicit when dealing with deferred execution? I run into very few cases where an infinite timeout period makes sense.
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komon
You're not the only person to be asking this question recently!

Kyle Simpson (@getify on twitter and github) of You Don't Know JS fame has
been working on a library for Javascript that wraps generators in a way that:

a) lets you use other Promise workflows to interact with them

b) lets you create a cancellation token that can be passed to a chain of
asynchronous work to allow jobs to be cancelled all the way down that chain

among other goodies. Even if you're not working in the JS space, it's some
really cool work to read about[1]

[1][https://github.com/getify/CAF](https://github.com/getify/CAF)

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0x0aff374668
Whoa. That's brilliant. Thanks!

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SamReidHughes
Well, you have to cancel the task, not ignore it. So you need some standard
cancellation hook. And that generally has to be something explicitly handled
by the task in question; it cannot automatically percolate all the way down to
the deepest sub-task.

If your promise lib has cancellation built in, then adding a timeout to one is
easy.

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0x0aff374668
oh, shit. that means if i just send a timeout promise and a worker promise to
Promise.race([...]), and the timeout finishes but the worker never does...
then I have some unfulfilled promise hanging out somewhere indefinitely? I
guess so... if I do Promise.race([p1, p2]) and p1 fulfills and p2 doesn't, p2
is still alive...indefinitely. Am I right or wrong...?

