js-on-sx: object literal spread {...src}

lib/js/runtime.sx

@@ -3477,6 +3477,55 @@
         (dict-set! obj sk val)
         val))))
 
+(define
+  js-obj-spread!
+  (fn
+    (target src)
+    (cond
+      ((or (= src nil) (js-undefined? src)) target)
+      ((dict? src)
+        (begin
+          (for-each
+            (fn
+              (k)
+              (if
+                (js-key-internal? k)
+                nil
+                (js-obj-set! target k (get src k))))
+            (js-object-keys src))
+          target))
+      ((= (type-of src) "string")
+        (let
+          ((n (len src)))
+          (begin (js-obj-spread-string-loop! target src 0 n) target)))
+      ((list? src)
+        (let
+          ((n (len src)))
+          (begin (js-obj-spread-list-loop! target src 0 n) target)))
+      (else target))))
+
+(define
+  js-obj-spread-string-loop!
+  (fn
+    (target s i n)
+    (cond
+      ((>= i n) nil)
+      (else
+        (begin
+          (js-obj-set! target (js-to-string i) (char-at s i))
+          (js-obj-spread-string-loop! target s (+ i 1) n))))))
+
+(define
+  js-obj-spread-list-loop!
+  (fn
+    (target arr i n)
+    (cond
+      ((>= i n) nil)
+      (else
+        (begin
+          (js-obj-set! target (js-to-string i) (nth arr i))
+          (js-obj-spread-list-loop! target arr (+ i 1) n))))))
+
 (begin
   (define
     js-set-prop