Change ' replacement string to _2

generator/js_of_ast.ml

@@ -236,12 +236,12 @@ let ppf_pat_array id_list array_expr =
 let ppf_field_access expr field =
   Printf.sprintf "%s.%s" expr field
 
-(* ' is not permitted in JS identifier names, and $ is not permitted in OCaml ones *)
+(* ' is not permitted in JS identifier names, we assume _2 is not used in OCaml names *)
 let ppf_ident_name x =
-  if List.mem x ["arguments"]
+  if List.mem x ["arguments"; "eval"; "caller"]
     then unsupported ("use of reserved keyword: " ^ x);
       (* TODO: complete the list *)
-  String.map (function '\'' -> '$' | c -> c) x
+  Str.global_replace (Str.regexp "'") "_2" x
 
 let ppf_ident i =
   i |> Ident.name |> ppf_ident_name