I've got a list of ISO 8601-compatible strings, some of which are dates (like '2022-12-25'), some are date-time values (like '2022-12-25T12:00'), and some have time zone info (like '2022-12-25T12:00-08:00[America/Los_Angeles]'.
Using the new Temporal API that's coming to JavaScript, is there one function I can call to parse all these strings into their corresponding Temporal types like Temporal.PlainDate, Temporal.PlainDateTime, Temporal.ZonedDateTime, etc.?
No, there is not a universal parse-into-any-Temporal-type function that's built into the language.
This is because the same string can be used to parse many different Temporal types.
To parse a string into a Temporal type, you must know ahead of time what type you want.
For example, 2020-04-25[u-ca=hebrew] can be successfully parsed by Temporal.PlainDate.from, Temporal.PlainMonthDay.from, Temporal.PlainYearMonth.from, or even Temporal.PlainDateTime.from.
This ambiguity requires choosing a Temporal type before parsing.
If you have a list of date/time strings and you don't know what type they are, but you'd like to parse them anyways, then it's fairly straightforward to write a function that calls the from methods of multiple Temporal types and returns the first result that doesn't throw. Just make sure to only include types that contain all the data you require, and make sure to put the types in order from "most data" to "least data" in the string. This will usually be this order:
Temporal.ZonedDateTime
Temporal.Instant
Temporal.PlainDateTime
Temporal.PlainDate
Temporal.PlainTime
Temporal.PlainYearMonth
Temporal.PlainMonthDay
Temporal.Duration (although honestly I doubt that there are many use cases where both duration data and date/time data is combined in the same input!)
If you're curious about why Temporal doesn't have a Temporal.parse method, more background can be found here: https://tc39.es/proposal-temporal/docs/parse-draft.html (I'm one of the champions of the Temporal proposal since 2020.) Here's one relevant excerpt:
This is a draft design document for a
Temporal.parseAPI, which is not currently planned to be implemented for several reasons:
Temporal's approach to most operations—including parsing—is to encourage strong typing, e.g.Temporal.Instant.fromvs.Temporal.PlainDateTime.from. A type-spanning "parse anything" API goes against that strongly-typed model.- The main use case beyond type-specific parsing that was identified for a
parseAPI was handling "partially correct" ISO strings, e.g. where only one unit was out of range. Most of these use cases were addressed via theoverflowoption in thefrommethod of all types which either clamps out-of-range values ('constrain') to the nearest in-range value or throws ('reject') in that case.- The final remaining case for a
parseAPI was resolving the case where a time zone and a time zone offset can be in conflict, as would happen for futureTemporal.ZonedDateTimevalues stored before a country permanently abolishes DST. This use case is now handled via theoffsetoption ofTemporal.ZonedDateTime.from.
Temporal.parse() function to return the most specific type that can be created from the string, so a PlainDate from 2020-04-25, PlainMonthDay from 04-25, and PlainYearMonth from 2020-04
Temporal.parse with that behavior, it'd be much more easily discoverable via IDE autocomplete than the type-specific parsing methods like Temporal.PlainDate.from. Many novice developers would likely end up using that method and assuming the result would always be the type they expect. Then they'd lose the ability to easily detect unexpected data in the input. This would likely lead to fragile code, and could even undermine one of the main benefits of Temporal which is for users to use a specific Temporal type for a specific kind of input data.Temporal.parse method at tc39.es/proposal-temporal/docs/parse-draft.html, including some explanations of alternatives considered and why we decided not to include it in the proposal. (I've been one of the Temporal proposal's champions on TC39 since 2020.)