⏱️ Use these `:timer` helpers to remove magic ms numbers

Notes

Many functions in Elixir take milliseconds as an argument.

Take Process.sleep/1 as an example:

Process.sleep(300_000)

🤨 Uh… that’s okay, but unless you know how to read the Matrix, it’s hard to know (at a glance) what 300_000 ms is in a more sensible unit.

Typically what I do is add clarity by creating a module attribute:

@five_minutes 1000 * 60 * 5

# in a function
Process.sleep(@five_minutes)

It’s easier to see that we’re passing data in milliseconds (the 1000), and we can see clearly that it’s 60 seconds times 5 (i.e. 5 minutes).

But there’s an even better way – and I only just learned about it recently.

Erlang’s :timer module has three functions to help us with this very issue:

iex> :timer.minutes(5)
# => 300000

iex> :timer.seconds(5)
# => 5000

iex> :timer.hours(5)
# => 18000000

That’ll make our code sooo clear!