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Comment by iforgotpassword | Hacker News Reader

Can someone explain the node version to me? My js knowledge is from a decade ago. AFAIK, setTimeout creates a timer and returns a handle to it. What does promisify do? I'd assume it's a general wrapper that takes a function that returns X and wraps it so that it returns Promise<X>. So that code actually runs 10k tasks that each create a timer with a timeout of 10 seconds and return immediately.

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Promisify converts a callback based function into a promise returning function [1]. If the function has a `promisify.custom` method, `promisify` will simply return the `promisify.custom` method instead of wrapping the original function. Calling `promisify` on `setTimeout` in Node is redundant because Node already ships a built in promisified version of `setTimeout`. So the following is true:

  setTimeout[promisify.custom] === require('node:timers/promises').setTimeout

You could of course manually wrap `setTimeout` yourself as well:

  const sleep = n => new Promise(resolve => setTimeout(resolve, n))

[1] https://nodejs.org/docs/latest-v22.x/api/util.html#utilpromi...

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