There's many JS implementations out there. Quality kind depends on what you need, and there's some engines more or less complete in which quirks are supported.
And for example, v8 doesn't make much sense in embedded contexts
There are definitely plenty of other JS engines, but they aren't always up to date on newer JS features. I'm pretty sure this is the 3rd JS engine to fully support the Temporal API (even JSC hasn't shipped it yet).