Lots of surprises here! The general theme seems to be that the parser is very eager to find some interpretation of the input as a date, even in ways that appear pretty unprincipled, even in circumstances where human users would probably not agree with the interpretation, and even though it does have ways that it could signal errors. Though maybe some of the weird cases actually do trace back to unusual real-world use cases!
Yeah this is the curse of the intermediate developer at work
The junior developer experiences nothing but errors, and struggles to get something over the line
The intermediate developer adopts “reduce errors at all cost” mentality and their parsers are too helpful, they make too many assumptions, and you end up with the Date class type behaviour.
The senior developer knows the deadliness of this, and designs a robust class that behaves consistently and errors early on invalid input.
I'm not sure if I should be pleased or embarrassed about my 17/28. Why do I even know this?
My son was pretty happy with his 11/28 without any experience with js Date. Just deduced it from previous answers. And I explained type coercion to him.
I now realize I may have put him off a career in IT.
At the beginning of the quiz, the author noted the exact time zone their laptop is in, have at least one of the questions I got wrong because I didn't take that into account. Totally valid though, and I honestly felt like I should have recognized that it would come into play given how I noticed how specific it was before starting
Always fun to click through JS quizzes for the laughs. I've been programming JS since over a decade, and I never dared to use Date to parse anything I didn't verify with a regex.
i coded security js code for a decade. right when the standard started to get the many updates.
our system was just a really tiny subset of things you could use that worked safely (and predictably) across browsers. even after the updates, we only incorporated was array.filter and structuredcopy. everything else offered no real benefit and only added to the attack surface.
and then came typescript. the biggest missed opportunity in js history.
even today, good js is knowing you can only use 1% of the language, and even that with lot of care
It's a fun quiz, and there's a lot of surprising behaviour. However in my opinion from a practical perspective it mostly doesn't matter.
Think hard about whether your use case really cares about local time, try and find ways to make instants appropriate. Then stick to UTC ISO 8601 strings / Unix timestamps and most of the complexity goes away, or at least gets contained to a small part of your software.
I know this isn't always possible (I once had to support a feature that required the user took a break covering two periods of 1-5am local, which was obviously fun around DST boundaries) - but in my experience at least the majority of the time you can find ways to minimise the surface area that cares.
If you're passing raw/unvalidated user input to the date parser you're holding it wrong.
I just fixed a bug at work where JS Date was parsing arbitrarily long strings as random date values just because they happened to contain an integer anywhere in the string. Madness.
In a language which doesn't understand that "false" isn't true? I would be entirely unsurprised to discover it's secretly calling a browser vendor web API to search for similarly named dates, or that it's now AI powered and might decide "Last Christmas" means the release date (December 3 1984) of the single not like, Christmas Day in 2024...
I think after the 1970s "Worse is better" languages vanish from the Earth the last shadow of that thinking left might be Javascript, hopefully by then humans aren't writing it but of course for "compatibility" it'll still be implemented by web browsers.
Since the website says "All questions verified using NodeJS 24.4.0" and that all string parsing made by the Date constructor is define in ECMAScript to follow ISO 8601 plus being engine specific, the sub headline should say: How well do you know V8's Date parsing?
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[ 3.2 ms ] story [ 59.6 ms ] threadBurn it and start again.
The junior developer experiences nothing but errors, and struggles to get something over the line
The intermediate developer adopts “reduce errors at all cost” mentality and their parsers are too helpful, they make too many assumptions, and you end up with the Date class type behaviour.
The senior developer knows the deadliness of this, and designs a robust class that behaves consistently and errors early on invalid input.
Usually I can overcome that urge. It's curious that these designers could not.
My son was pretty happy with his 11/28 without any experience with js Date. Just deduced it from previous answers. And I explained type coercion to him.
I now realize I may have put him off a career in IT.
Chrome is implementing it[2]
WebKit has an open PR[3]
I found no reference to Node working on it
and of course you can already use a polyfill (though it's quite heavy)
[1] https://deno.com/blog/v1.40?ref=computus.org#temporal-api
[2] https://chromestatus.com/feature/5668291307634688?ref=comput...
[3] https://github.com/WebKit/WebKit/pull/45603
Thanks!
i coded security js code for a decade. right when the standard started to get the many updates.
our system was just a really tiny subset of things you could use that worked safely (and predictably) across browsers. even after the updates, we only incorporated was array.filter and structuredcopy. everything else offered no real benefit and only added to the attack surface.
and then came typescript. the biggest missed opportunity in js history.
even today, good js is knowing you can only use 1% of the language, and even that with lot of care
Adding Temporal will only add to the chaos. Now there will be Date, moment, Luxon’s objects, and Temporal. See??? We fixed it!!!
Think hard about whether your use case really cares about local time, try and find ways to make instants appropriate. Then stick to UTC ISO 8601 strings / Unix timestamps and most of the complexity goes away, or at least gets contained to a small part of your software.
I know this isn't always possible (I once had to support a feature that required the user took a break covering two periods of 1-5am local, which was obviously fun around DST boundaries) - but in my experience at least the majority of the time you can find ways to minimise the surface area that cares.
If you're passing raw/unvalidated user input to the date parser you're holding it wrong.
Dates and times are insane, no matter the language.
I think my strategy for JavaScript going forward is to 'drop & run'.
I think after the 1970s "Worse is better" languages vanish from the Earth the last shadow of that thinking left might be Javascript, hopefully by then humans aren't writing it but of course for "compatibility" it'll still be implemented by web browsers.
I'm not sure if it's caused by JavaScript quirkiness under the hood or a bug in the library, but it's mindblowing.