Parser: jp-parse-postfix emits (js-postfix op target) on trailing ++/--; jp-parse-primary emits (js-prefix op target) before the unary -/+/!/~ branch. Transpile: js-transpile-prefix → (set! name (+ (js-to-number name) ±1)) for idents, (js-set-prop obj key ...) for members/indices. js-transpile-postfix caches old value in a let binding, updates, returns the saved value. 340/342 unit (+11), 148/148 slice unchanged.