js-on-sx: postfix + prefix ++/--

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.

plans/js-on-sx.md

@@ -175,7 +175,9 @@ Append-only record of completed iterations. Loop writes one line per iteration:
 
 - 2026-04-23 — **Regex literal support (lex+parse+transpile+runtime stub).** Runner now accepts repeatable `--filter` flags (OR'd). Lexer gains `js-regex-context?` (returns true at SOF or when last token is op/non-closing-punct/regex-keyword incl. return/typeof/in/of/throw/new/delete/instanceof/void/yield/await/case/do/else) and `read-regex` (handles `\` escapes and `[...]` classes, collects flags as ident chars). `scan!` intercepts `/` ahead of the operator-match tries when in a regex context and emits `{:type "regex" :value {:pattern :flags}}`. Parser adds a `regex` primary branch → `(js-regex pat flags)`. Transpile emits `(js-regex-new pat flags)`. Runtime adds: `js-regex?` predicate (dict + `__js_regex__` key), `js-regex-new` builds the tagged dict with `source / flags / global / ignoreCase / multiline / sticky / unicode / dotAll / hasIndices / lastIndex` populated; `js-regex-invoke-method` dispatches `.test` / `.exec` / `.toString`; `js-invoke-method` gets a regex branch before the generic method-lookup fallback. Stub engine (`js-regex-stub-test` / `-exec`) uses `js-string-index-of` — not a real regex, but enough to make `/foo/.test('hi foo')` work. `__js_regex_platform__` dict + `js-regex-platform-override!` let a real platform primitive be swapped in later without runtime changes. 30 new unit tests (17 lex + 3 parse + 1 transpile + 4 obj-shape + 4 prop + 2 test()): **308/310** (278→+30). Conformance unchanged. Gotcha: `contains?` with 2 args expects `(contains? list x)`, NOT a dict — use `(contains? (keys d) k)` or `dict-has?`. First pass forgot that and cascaded errors across Math / class tests via the `js-regex?` predicate inside `js-invoke-method`. Wide scoreboard run across 9 targeted categories launched in background.
 
-- 2026-04-23 — **Expanded Math + Number globals.** Added `Math.sqrt/.pow/.trunc/.sign/.cbrt/.hypot` using SX primitives (`sqrt`, `pow`, `abs`, hand-rolled loops). Added missing constants: `Math.LN2 / LN10 / LOG2E / LOG10E / SQRT2 / SQRT1_2`; bumped PI/E precision to full 16-digit. New `Number` global: `isFinite`, `isNaN`, `isInteger`, `isSafeInteger`, `MAX_VALUE / MIN_VALUE / MAX_SAFE_INTEGER / MIN_SAFE_INTEGER / EPSILON / POSITIVE_INFINITY / NEGATIVE_INFINITY / NaN`. Global `isFinite`, `isNaN`, `Infinity`, `NaN`. `js-number-is-nan` uses the self-inequality trick `(and (number? v) (not (= v v)))`. Wired into `js-global`. 21 new unit tests (12 Math + 9 Number), **329/331** (308→+21). Conformance unchanged. Gotchas: (1) `sx_insert_near` takes a single node — multi-define source blocks get silently truncated. Use `sx_insert_child` at the root per define. (2) SX `(/ 1 0)` → `inf`, and `1e999` also → `inf`; both can be used as `Infinity`. (3) `1e999` has no `-` form — wrap as `(- 0 1e999)` or just use `-1e999` literal.
+- 2026-04-23 — **Expanded Math + Number globals.** Added `Math.sqrt/.pow/.trunc/.sign/.cbrt/.hypot` using SX primitives (`sqrt`, `pow`, `abs`, hand-rolled loops). Added missing constants: `Math.LN2 / LN10 / LOG2E / LOG10E / SQRT2 / SQRT1_2`; bumped PI/E precision to full 16-digit. New `Number` global: `isFinite`, `isNaN`, `isInteger`, `isSafeInteger`, `MAX_VALUE / MIN_VALUE / MAX_SAFE_INTEGER / MIN_SAFE_INTEGER / EPSILON / POSITIVE_INFINITY / NEGATIVE_INFINITY / NaN`. Global `isFinite`, `isNaN`, `Infinity`, `NaN`. `js-number-is-nan` uses the self-inequality trick `(and (number? v) (not (= v v)))`. Wired into `js-global`. 21 new unit tests (12 Math + 9 Number), **329/331** (308→+21). Conformance unchanged. Gotchas: (1) `sx_insert_near` takes a single node — multi-define source blocks get silently truncated. Use `sx_insert_child` at the root per define. (2) SX `(/ 1 0)` → `inf`, and `1e999` also → `inf`; both can be used as `Infinity`. (3) **`(define NaN ...)` and `(define Infinity ...)` crash at load — SX tokenizer parses `NaN` and `Infinity` as the *numeric literals* `nan` / `inf`, so `define` sees `(define <number> <value>)` and rejects it with "Expected symbol, got number". Drop those top-level aliases; put the values in `js-global` dict instead where the keyword key avoids the conflict.**
+
+- 2026-04-23 — **Postfix/prefix `++` / `--`.** Parser: postfix branch in `jp-parse-postfix` (matches `op ++`/`--` after the current expression and emits `(js-postfix op target)`), prefix branch in `jp-parse-primary` *before* the unary-`-/+/!/~` path emits `(js-prefix op target)`. Transpile: `js-transpile-prefix` emits `(set! sxname (+ (js-to-number sxname) ±1))` for idents, `(js-set-prop obj key (+ (js-to-number (js-get-prop obj key)) ±1))` for members/indices. `js-transpile-postfix` uses a `let` binding to cache the old value via `js-to-number`, then updates and returns the saved value — covers ident, member, and index targets. 11 new unit tests (ident inc/dec, pre vs post return value, obj.key, a[i], in `for(;; i++)`, accumulator loop), **340/342** (329→+11). Conformance unchanged.
 
 ## Phase 3-5 gotchas