moment.creationData() replacement ?

I want to get the `format` of a dayjs instance. Is there a similar method like creationDate() provided by moment?

```
moment("2013-01-02", "YYYY-MM-DD", true).creationData() === {
input: "2013-01-02",
format: "YYYY-MM-DD",
locale: Locale obj,
isUTC: false,
strict: true
}
```

No file, test, or entry point is named. Start by locating the Day.js parsing and instance API, then compare the available state with the Moment creationData() fields shown in the issue. Done means a documented equivalent can expose the requested input, format, locale, UTC, and strictness information.

Written by the indexing model from the issue text.