js-on-sx: String.fromCharCode + parseInt + parseFloat

String global with fromCharCode (variadic). parseInt truncates via
js-math-trunc; parseFloat delegates to js-to-number. Wired into
js-global.

381/383 unit (+5), 148/148 slice unchanged.

lib/js/runtime.sx

@@ -1608,6 +1608,34 @@
 
 (define Array {:isArray js-array-is-array :of js-array-of})
 
+(define
+  js-string-from-char-code
+  (fn (&rest args) (js-string-from-char-code-loop args 0 "")))
+
+(define
+  js-string-from-char-code-loop
+  (fn
+    (args i acc)
+    (if
+      (>= i (len args))
+      acc
+      (js-string-from-char-code-loop
+        args
+        (+ i 1)
+        (str acc (js-code-to-char (js-num-to-int (nth args i))))))))
+
+(define String {:fromCharCode js-string-from-char-code})
+
+(define
+  parseInt
+  (fn
+    (&rest args)
+    (if (= (len args) 0) 0 (js-math-trunc (js-to-number (nth args 0))))))
+
+(define
+  parseFloat
+  (fn (&rest args) (if (= (len args) 0) 0 (js-to-number (nth args 0)))))
+
 (define
   js-promise-flush-callbacks!
   (fn
@@ -2022,4 +2050,4 @@
         (str "/" (get rx "source") "/" (get rx "flags")))
       (else js-undefined))))
 
-(define js-global {:isFinite js-global-is-finite :console console :Number Number :Math Math :Array Array :NaN 0 :Infinity inf :isNaN js-global-is-nan :Object Object :undefined js-undefined})
+(define js-global {:isFinite js-global-is-finite :console console :Number Number :Math Math :Array Array :String String :NaN 0 :Infinity inf :isNaN js-global-is-nan :Object Object :undefined js-undefined})