1401406 - Different MDN docs claim contradictory definitions about performance.timeOrigin

Status: RESOLVED WONTFIX

(Developer Documentation Graveyard :: API: Miscellaneous, enhancement)

Description

[Dan Mosedale (:dmosedale, :dmose)]

https://developer.mozilla.org/en-US/docs/Web/API/Performance/now

describes it as 

"the time origin (the PerformanceTiming.navigationStart property)."

The DOMHighResTimeStamp page, has a [much more complex definition](https://developer.mozilla.org/en-US/docs/Web/API/DOMHighResTimeStamp#The_time_origin).

This makes using performance.timeOrigin in JavaScript code for some things difficult.

I'm guessing that this conflict is because the W3C standards changed over time.
It would helpful to know which versions of Firefox have which implementations (assuming one of them isn't just wrong).

Comment 1

[Dan Mosedale (:dmosedale, :dmose)]

Excitingly, there seem to be two different usages in the tree:

http://searchfox.org/mozilla-central/source/dom/performance/PerformanceService.cpp#33
http://searchfox.org/mozilla-central/source/dom/base/nsDOMNavigationTiming.h#117

meaning that it's at least conceivable that both of those documents are sort-of right.

Comment 2

[Dan Mosedale (:dmosedale, :dmose)]

(Except for the part where they're inconsistent with each other, I think).

Comment 3

[Dan Mosedale (:dmosedale, :dmose)]

Just poking at the web console on a random web page, evidence would seem to suggest that at least for one case, it's not as simple as the performance.now() MDN page claims, as here we see different timeOrigin and navigationStart properties:

> performance
Performance { timeOrigin: 1505861544822.1272, ... }
> performance.timing
PerformanceTiming { navigationStart: 1505865402719, ... }

Comment 4

[Dan Mosedale (:dmosedale, :dmose)]

That last test was on Nightly 57.0a1 (2017-09-19) (64-bit) on Mac.

Comment 5

[Chris Mills [:cmills]]

Hi Dan,

Thanks for bringing this up. I've had a read of the specs, and it looks like the origin time definition here is correct:

https://developer.mozilla.org/en-US/docs/Web/API/DOMHighResTimeStamp#The_time_origin

But I wasn't satisfied with the definition at the other document (e.g. time origin isn't just the same as navigationStart). So I've updated it to just point to the one I think is correct - see it now:

https://developer.mozilla.org/en-US/docs/Web/API/Performance/now

Do you think this fixes the problem, or do you think more needs to be done?

Comment 6

[BMO Automation]

MDN Web Docs' bug reporting has now moved to GitHub. From now on, please file content bugs at https://github.com/mdn/sprints/issues/ and platform bugs at https://github.com/mdn/kuma/issues/.