diff --git a/lib/js/runtime.sx b/lib/js/runtime.sx
index ba77a18f..6ddeec1a 100644
--- a/lib/js/runtime.sx
+++ b/lib/js/runtime.sx
@@ -202,6 +202,24 @@
             (js-to-string key)
             " is not a function (on number)"))))))
 
+(define
+  js-invoke-function-objproto
+  (fn
+    (recv key args)
+    (cond
+      ((= key "hasOwnProperty")
+        (let
+          ((k (if (empty? args) "" (js-to-string (nth args 0)))))
+          (or (= k "name") (= k "length") (= k "prototype"))))
+      ((= key "toString") "function () { [native code] }")
+      ((= key "valueOf") recv)
+      ((= key "isPrototypeOf") false)
+      ((= key "propertyIsEnumerable") false)
+      ((= key "toLocaleString") "function () { [native code] }")
+      (else :js-undefined))))
+
+;; ── String coercion (ToString) ────────────────────────────────────
+
 (define
   js-invoke-boolean-method
   (fn
@@ -216,8 +234,6 @@
             (js-to-string key)
             " is not a function (on boolean)"))))))
 
-;; ── String coercion (ToString) ────────────────────────────────────
-
 (define
   js-num-to-str-radix
   (fn
@@ -236,6 +252,9 @@
             (str "-" (js-num-to-str-radix-rec (- 0 int-n) radix ""))
             (js-num-to-str-radix-rec int-n radix "")))))))
 
+;; ── Arithmetic (JS rules) ─────────────────────────────────────────
+
+;; JS `+`: if either operand is a string → string concat, else numeric.
 (define
   js-num-to-str-radix-rec
   (fn
@@ -247,9 +266,6 @@
         ((d (mod n radix)) (rest (js-math-trunc (/ n radix))))
         (js-num-to-str-radix-rec rest radix (str (js-digit-char d) acc))))))
 
-;; ── Arithmetic (JS rules) ─────────────────────────────────────────
-
-;; JS `+`: if either operand is a string → string concat, else numeric.
 (define
   js-digit-char
   (fn
@@ -349,6 +365,8 @@
             ((not (js-undefined? m)) (js-call-with-this recv m args))
             ((and (js-function? recv) (js-function-method? key))
               (js-invoke-function-method recv key args))
+            ((and (js-function? recv) (js-object-builtin-method? key))
+              (js-invoke-function-objproto recv key args))
             ((and (= (type-of recv) "dict") (js-object-builtin-method? key))
               (js-invoke-object-method recv key args))
             (else
@@ -367,6 +385,7 @@
       (= name "valueOf")
       (= name "toLocaleString"))))
 
+;; Bitwise + logical-not
 (define
   js-invoke-object-method
   (fn
@@ -388,14 +407,13 @@
       ((= name "toLocaleString") "[object Object]")
       (else js-undefined))))
 
-;; Bitwise + logical-not
 (define js-upper-case (fn (s) (js-case-loop s 0 "" true)))
 
-(define js-lower-case (fn (s) (js-case-loop s 0 "" false)))
-
 ;; ── Equality ──────────────────────────────────────────────────────
 
 ;; Strict equality (===): no coercion; js-undefined matches js-undefined.
+(define js-lower-case (fn (s) (js-case-loop s 0 "" false)))
+
 (define
   js-case-loop
   (fn
@@ -411,6 +429,9 @@
               ((cv (cond ((and to-upper? (>= cc 97) (<= cc 122)) (js-code-to-char (- cc 32))) ((and (not to-upper?) (>= cc 65) (<= cc 90)) (js-code-to-char (+ cc 32))) (else c))))
               (js-case-loop s (+ i 1) (str acc cv) to-upper?))))))))
 
+;; Abstract equality (==): type coercion rules.
+;; Simplified: number↔string coerce both to number; null == undefined;
+;; everything else falls back to strict equality.
 (define
   js-code-to-char
   (fn
@@ -470,13 +491,15 @@
       ((= code 122) "z")
       (else ""))))
 
-;; Abstract equality (==): type coercion rules.
-;; Simplified: number↔string coerce both to number; null == undefined;
-;; everything else falls back to strict equality.
 (define
   js-invoke-method-dyn
   (fn (recv key args) (js-invoke-method recv key args)))
 
+;; ── Relational comparisons ────────────────────────────────────────
+
+;; Abstract relational comparison from ES5.
+;; Numbers compare numerically; two strings compare lexicographically;
+;; mixed types coerce both to numbers.
 (define
   js-call-plain
   (fn
@@ -488,11 +511,6 @@
         (js-call-with-this :js-undefined (get fn-val "__callable__") args))
       (else (js-call-with-this :js-undefined fn-val args)))))
 
-;; ── Relational comparisons ────────────────────────────────────────
-
-;; Abstract relational comparison from ES5.
-;; Numbers compare numerically; two strings compare lexicographically;
-;; mixed types coerce both to numbers.
 (define
   js-new-call
   (fn
@@ -572,6 +590,13 @@
           nil)
         this))))
 
+;; ── Property access ───────────────────────────────────────────────
+
+;; obj[key] or obj.key in JS. Handles:
+;;   • dicts keyed by string
+;;   • lists indexed by number (incl. .length)
+;;   • strings indexed by number (incl. .length)
+;; Returns js-undefined if the key is absent.
 (define
   TypeError
   (fn
@@ -590,13 +615,6 @@
           nil)
         this))))
 
-;; ── Property access ───────────────────────────────────────────────
-
-;; obj[key] or obj.key in JS. Handles:
-;;   • dicts keyed by string
-;;   • lists indexed by number (incl. .length)
-;;   • strings indexed by number (incl. .length)
-;; Returns js-undefined if the key is absent.
 (define
   RangeError
   (fn
@@ -633,6 +651,7 @@
           nil)
         this))))
 
+;; Setter — mutates the dict. Returns the new value (JS assignment yields rhs).
 (define
   ReferenceError
   (fn
@@ -651,7 +670,10 @@
           nil)
         this))))
 
-;; Setter — mutates the dict. Returns the new value (JS assignment yields rhs).
+;; ── Short-circuit logical ops ─────────────────────────────────────
+
+;; `a && b` in JS: if a is truthy return b else return a. The thunk
+;; form defers evaluation of b — the transpiler passes (fn () b).
 (define
   js-function?
   (fn
@@ -664,19 +686,17 @@
         (= t "component")
         (and (= t "dict") (contains? (keys v) "__callable__"))))))
 
-;; ── Short-circuit logical ops ─────────────────────────────────────
-
-;; `a && b` in JS: if a is truthy return b else return a. The thunk
-;; form defers evaluation of b — the transpiler passes (fn () b).
 (define __js_proto_table__ (dict))
 
-(define __js_next_id__ (dict))
-
 ;; ── console.log ───────────────────────────────────────────────────
 
 ;; Trivial bridge. `log-info` is available on OCaml; fall back to print.
+(define __js_next_id__ (dict))
+
 (dict-set! __js_next_id__ "n" 0)
 
+;; ── Math object ───────────────────────────────────────────────────
+
 (define
   js-get-ctor-proto
   (fn
@@ -687,9 +707,6 @@
         ((dict-has? __js_proto_table__ id) (get __js_proto_table__ id))
         (else
           (let ((p (dict))) (begin (dict-set! __js_proto_table__ id p) p)))))))
-
-;; ── Math object ───────────────────────────────────────────────────
-
 (define
   js-reset-ctor-proto!
   (fn
@@ -764,7 +781,8 @@
         (else (js-nan-value))))))
 (define
   js-is-numeric-string?
-  (fn (s) (js-is-numeric-loop s 0 false false false)))
+  (fn (s) (js-is-numeric-loop s 0 false false false)))   ; deterministic placeholder for tests
+
 (define
   js-is-numeric-loop
   (fn
@@ -792,14 +810,14 @@
                   (or (= prev "e") (= prev "E"))
                   (js-is-numeric-loop s (+ i 1) sawdigit sawdot sawe)
                   false)))
-            (else false)))))))   ; deterministic placeholder for tests
-
-(define js-parse-num-safe (fn (s) (cond (else (js-num-from-string s)))))
+            (else false)))))))
 
 ;; The global object — lookup table for JS names that aren't in the
 ;; SX env. Transpiled idents look up locally first; globals here are a
 ;; fallback, but most slice programs reference `console`, `Math`,
 ;; `undefined` as plain symbols, which we bind as defines above.
+(define js-parse-num-safe (fn (s) (cond (else (js-num-from-string s)))))
+
 (define
   js-num-from-string
   (fn