til/javascript/sleep-for-a-bit-in-async-code.md

Sleep For A Bit In Async Code

A sleep utility function can be useful in a variety of situations. From testing and debugging to simulating a delay in development.

Here is what that function can look like in its simplest form:

function sleep(time) {
  return new Promise((resolve) => {
    setTimeout(resolve, time)
  })
}

This function returns a promise that will resolve after the given number of milliseconds.

As an example of how to use it, here is how we can simulate a delay in a fake fetch function.

async function fakeUserFetch(userId) {
  # add half a second of "network" latency
  await sleep(500)

  const fakeResponse = {
    id: userId,
    email: "fake-email@example.com"
  }

  return Promise.resolve(fakeResponse)
}

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