js.el: Tweak last change

* lisp/progmodes/js.el (js-json-mode): Use a function as value of
`syntax-propertize-function`.

diff --git a/lisp/progmodes/js.el b/lisp/progmodes/js.el
index d2c24a75810a943075cf8a02db63f642f0c74866..efad3b52aa9f0a5808aad72aaf677da7d9838edb 100644 (file)
--- a/lisp/progmodes/js.el
+++ b/lisp/progmodes/js.el
@@ -3490,9 +3490,10 @@ This function is intended for use in `after-change-functions'."
 
 ;;;###autoload
 (define-derived-mode js-json-mode js-mode "JSON"
-  ;; JSON files can be big.  Speed up syntax-ppss.
-  (setq-local syntax-propertize-function nil)
-  (setq-local js-enabled-frameworks nil))
+  (setq-local js-enabled-frameworks nil)
+  ;; Speed up `syntax-ppss': JSON files can be big but can't hold
+  ;; regexp matchers nor #! thingies (and `js-enabled-frameworks' is nil).
+  (setq-local syntax-propertize-function #'ignore))
 
 ;; Since we made JSX support available and automatically-enabled in
 ;; the base `js-mode' (for ease of use), now `js-jsx-mode' simply