Implement HTML standard timer APIs

[MylesBorins]

As documented in https://html.spec.whatwg.org/multipage/timers-and-user-prompts.htm

@bdougie brought this in #27 (comment)

This would include:

setTimeout()
setInterval()
clearTimeout()
clearInterval()

In deno this is how it is implemented

https://github.com/denoland/deno/blob/master/cli/global_timer.rs
https://github.com/denoland/deno/blob/master/cli/rt/11_timers.js

Definitely interesting that the JavaScript runtime extensions are implemented in deno_cli not deno_core

[devsnek]

Can we do a promise version instead?

[MylesBorins]

@devsnek we could, although I will admit I fail to see value in creating a new timer API that is specific to JSTime. might be worth discussing with HTML + maybe node (deno?) if other platforms would be interested in a promise based API as well

[bengl]

Regardless of API, this would still be likely blocked by #12.

[bartlomieju]

Definitely interesting that the JavaScript runtime extensions are implemented in deno_cli not deno_core

As pointed by @bengl timers require event loop. deno_core is agnostic of event loop used and thus timer are implemented in deno_cli (and are built on top of Tokio). The whole timers code is quite complex at the moment because Tokio doesn't support ordered timers (tokio-rs/tokio#1775)

FYI - we'll be moving those APIs to a separate crate in near(-ish) future.

[devsnek]

for timers I would expect a thread with a timer wheel anyway, so not a huge issue for tokio to not be involved.