Is V8 Responsible for JavaScript Execution?

V8 can execute JavaScript code, but only pure functions. Do anything that doesn't interact with IO has to be handled by an external runtime. V8 is still the one that's keeping track of which promises exists and the code that is meant to be invoked when they resolve all that kind of thing. But the underlying infrastructure that actually invokes, which promises get resolved at what point in time, this is driven by the event loop,. So Dino, for example, it uses Tokyo for its event loop. This is an event loop written in Rust. It's very popular in the Rust ecosystem. Node uses libUV. This is a relatively popular run-time event loop implementation for C++