Design

Goals

Absolute compatibility

• all syntax should be valid JS
• absolutely no divergence in behavior from existing JS engines

Explicit opt-in

• should be able to provide console information when validation fails
• fallback behavior is execution in normal engine

Statelessness

• compiled code should carry no stateful environment
• should be forwards-compatible with possible API for pre-compiling Worker-sendable code or caching pre-compiled code

No pointless coercions

• literals should never have coercions
• as much as possible, avoid no-op coercions that only serve as annotations for the validator

No implicit coercions between int and double

• enforces desired performance model

No bailouts

• no operations should require dynamic guards that have to bail out to a different engine
• the only interface to ordinary JS should be through very explicit touch points:
• FFI function calls
• coercions of results of FFI function calls