QuickJS and SpiderMonkey in WASM don't use JIT though - they're both just interpreters.
WASM itself is often JIT'ed so a JS-to-WASM compiler that functions like the common JS baseline compilers would still get some benefit of JIT'ing even though the types available to the ICs in WASM may not be as useful as in JS.
WASM itself is often JIT'ed so a JS-to-WASM compiler that functions like the common JS baseline compilers would still get some benefit of JIT'ing even though the types available to the ICs in WASM may not be as useful as in JS.
https://cfallin.org/blog/2023/10/11/spidermonkey-pbl/#future... has some interesting ideas on enabling the SpiderMonkey baseline compiler for WASM and possibly using partial evaluation to see better types.