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Technically, Deno is V8 and only runs JavaScript.

Deno supports and encourages writing code in TypeScript but the way it works is: Deno bundles TypeScrit compiler, uses it to convert TypeScript to JavaScript and then executes the JavaScript.

It can also run JavaScript files directly.

Deno's runtime is a bunch of JavaScript APIs + TypeScript typings so that they can be understood by TypeScript code.

There's a great Software Engineering Daily podcast with Elio Rivero [0] (audio and transcript in link) that goes into depth on Deno, TypeScript, JavaScript support. It's interesting that compile time was the (TS) killer.

[0]: https://softwareengineeringdaily.com/2020/09/28/deno-and-typ...

Deno can run both JS and TS no problem.

In the manual the examples are all given in both JS and TS formats.