js-on-sx: Array.prototype forEach/map/filter honour thisArg + pass (v,i,arr)

lib/js/runtime.sx

@@ -2222,13 +2222,40 @@
             ((sep (if (= (len args) 0) "," (js-to-string (nth args 0)))))
             (js-list-join arr sep))))
       ((= name "concat") (fn (&rest args) (js-list-concat arr args)))
-      ((= name "map") (fn (f) (js-list-map-loop f arr 0 (list))))
+      ((= name "map")
+        (fn (&rest args)
+          (let
+            ((f (if (empty? args) :js-undefined (nth args 0)))
+              (this-arg
+                (cond
+                  ((< (len args) 2) js-global-this)
+                  ((js-undefined? (nth args 1)) js-global-this)
+                  ((= (nth args 1) nil) js-global-this)
+                  (else (nth args 1)))))
+            (js-list-map-loop f arr this-arg 0 (list)))))
       ((= name "filter")
-        (fn (f) (js-list-filter-loop f arr 0 (list))))
+        (fn (&rest args)
+          (let
+            ((f (if (empty? args) :js-undefined (nth args 0)))
+              (this-arg
+                (cond
+                  ((< (len args) 2) js-global-this)
+                  ((js-undefined? (nth args 1)) js-global-this)
+                  ((= (nth args 1) nil) js-global-this)
+                  (else (nth args 1)))))
+            (js-list-filter-loop f arr this-arg 0 (list)))))
       ((= name "forEach")
         (fn
-          (f)
-          (begin (js-list-foreach-loop f arr 0) js-undefined)))
+          (&rest args)
+          (let
+            ((f (if (empty? args) :js-undefined (nth args 0)))
+              (this-arg
+                (cond
+                  ((< (len args) 2) js-global-this)
+                  ((js-undefined? (nth args 1)) js-global-this)
+                  ((= (nth args 1) nil) js-global-this)
+                  (else (nth args 1)))))
+            (begin (js-list-foreach-loop f arr this-arg 0) js-undefined))))
       ((= name "reduce")
         (fn
           (&rest args)
@@ -2337,7 +2364,7 @@
         (fn
           (f)
           (let
-            ((mapped (js-list-map-loop f arr 0 (list))))
+            ((mapped (js-list-map-loop f arr js-global-this 0 (list))))
             (js-list-flat-loop mapped 1 (list)))))
       ((= name "findLast")
         (fn (f) (js-list-find-last-loop f arr (- (len arr) 1))))
@@ -2514,35 +2541,42 @@
 (define
   js-list-map-loop
   (fn
-    (f arr i acc)
+    (f arr this-arg i acc)
     (cond
       ((>= i (len arr)) acc)
       (else
         (do
-          (append! acc (f (nth arr i)))
-          (js-list-map-loop f arr (+ i 1) acc))))))
+          (append!
+            acc
+            (js-call-with-this this-arg f (list (nth arr i) i arr)))
+          (js-list-map-loop f arr this-arg (+ i 1) acc))))))
 
 (define
   js-list-filter-loop
   (fn
-    (f arr i acc)
+    (f arr this-arg i acc)
     (cond
       ((>= i (len arr)) acc)
       (else
         (do
           (let
             ((v (nth arr i)))
-            (if (js-to-boolean (f v)) (append! acc v) nil))
-          (js-list-filter-loop f arr (+ i 1) acc))))))
+            (if
+              (js-to-boolean (js-call-with-this this-arg f (list v i arr)))
+              (append! acc v)
+              nil))
+          (js-list-filter-loop f arr this-arg (+ i 1) acc))))))
 
 (define
   js-list-foreach-loop
   (fn
-    (f arr i)
+    (f arr this-arg i)
     (cond
       ((>= i (len arr)) nil)
       (else
-        (do (f (nth arr i)) (js-list-foreach-loop f arr (+ i 1)))))))
+        (do
+          (js-call-with-this this-arg f (list (nth arr i) i arr))
+          (js-list-foreach-loop f arr this-arg (+ i 1)))))))
 
 (define
   js-list-reduce-loop

plans/js-on-sx.md

@@ -158,6 +158,8 @@ Each item: implement → tests → update progress. Mark `[x]` when tests green.
 
 Append-only record of completed iterations. Loop writes one line per iteration: date, what was done, test count delta.
 
+- 2026-05-09 — **`Array.prototype.forEach`/`map`/`filter` honour `thisArg` and pass `(value, index, array)` to callback.** Was calling the callback with just `(value)` from a bare `(f x)` and ignoring the optional second `thisArg` parameter. Per spec, the callback receives `(value, index, array)` and `this` is `thisArg ?? globalThis` in non-strict. Updated the prototype methods to take `&rest args`, extract `thisArg` (defaulting to globalThis when null/undefined), and route through `js-call-with-this` with the full triple. Updated `js-list-foreach-loop` / `js-list-map-loop` / `js-list-filter-loop` accordingly. Result: built-ins/Array/prototype/forEach 2/30 → 9/30, filter 5/30 → 10/30. Array 18/30, Object 30/30, Map 18/30 unchanged. conformance.sh: 148/148.
+
 - 2026-05-09 — **`Map.prototype.forEach` / `Set.prototype.forEach` honour `thisArg` and pass `(value, key, collection)` to callback.** Was hardcoding `js-undefined` as the callback receiver and only passing `(value, key)`. Per spec, the callback receives `(value, key, collection)` and `this` is `thisArg ?? globalThis` in non-strict. Updated `js-map-do-foreach` / `js-set-do-foreach` to accept an optional `thisArg`, defaulting to `globalThis` when null/undefined; the prototype methods now route the second positional arg through. Result: built-ins/Map/prototype 11/30 → 13/30, built-ins/Set/prototype +similar. Map 18/30 holds. conformance.sh: 148/148.
 
 - 2026-05-09 — **`for…in` walks the prototype chain (with shadowing) but stops at native prototypes.** Was using `js-object-keys` which only returns own enumerable keys, so `for (k in instance)` only saw the instance's own properties — not inherited ones from `FACTORY.prototype`. Per spec, for-in walks the entire chain and yields each unique enumerable key once. Added `js-for-in-keys` + `js-for-in-walk` that iterate the chain, deduping via `contains?`. Stops at `Object.prototype` / `Array.prototype` / etc. since those carry "non-enumerable" methods we don't track property-attribute-wise — without this guard, `for (k in {})` would enumerate `toString`/`valueOf`/etc. Result: language/statements/for-in 10/30 → 12/30. Object 30/30, Array 18/30 unchanged. conformance.sh: 148/148.