[js] don't generate array access for keyword-fields (closes #7645)

this is fine for js

src/generators/genjs.ml

@@ -129,7 +129,7 @@ let valid_js_ident s =
 	with Exit ->
 		false
 
-let field s = if Hashtbl.mem kwds s || not (valid_js_ident s) then "[\"" ^ s ^ "\"]" else "." ^ s
+let field s = if not (valid_js_ident s) then "[\"" ^ s ^ "\"]" else "." ^ s
 let ident s = if Hashtbl.mem kwds s then "$" ^ s else s
 let check_var_declaration v = if Hashtbl.mem kwds2 v.v_name then v.v_name <- "$" ^ v.v_name
 

tests/optimization/src/TestJs.hx

@@ -494,13 +494,13 @@ class TestJs {
 
 	#if js_enums_as_arrays
 	@:js('
-		var _g = Type["typeof"]("");
+		var _g = Type.typeof("");
 		var v = _g[1] == 6 && _g[2] == String;
 		TestJs.use(v);
 	')
 	#else
 	@:js('
-		var _g = Type["typeof"]("");
+		var _g = Type.typeof("");
 		var v = _g._hx_index == 6 && _g.c == String;
 		TestJs.use(v);
 	')