[ext/web] Event.timeStamp is always 0

[lowlighter]

Version: Deno 1.42.4

Currently any Event.timeStamp is always set to 0

deno/ext/web/02_event.js

Line 156 in 472a370

timeStamp: 0,

The timeStamp read-only property of the Event interface returns the time (in milliseconds) at which the event was created.

https://developer.mozilla.org/en-US/docs/Web/API/Event/timeStamp

It should be set to performance.now() or similar to match more closely what is expected

Motivation
Make possible to test cases that requires this property to be non-zero:

const oldEvent = new Event()
await delay(5)
const lastEvent = new Event()
a.lastUpdated = oldEvent.timeStamp+1

a.addEventListener(event => {
  if (event.timeStamp < a.lastUpdated)
    return
  expect(event).toBe(lastEvent)
})

a.dispatchEvent(oldEvent)
a.dispatchEvent(lastEvent)

The above is not possible currently, because timeStamp property is readonly

[dsherret]

This is a documented spec deviation: https://docs.deno.com/runtime/manual/runtime/web_platform_apis#spec-deviations-1

#20191

[lowlighter]

Is there a specific motivation behind this spec deviation ?

[dsherret]

Performance: #20191

I feel like there should be some way to opt into this behaviour though

[lowlighter]

Yeah it'd be nice, or at least somehow expose the _attributes symbol so users are able to override properties from the event despite them being readonly

[lucacasonato]

Mh, I still wonder if we can re-implement this in some way...