docs snippets: a few more minor tweaks (#28225)

* Remove extra comma.

* Use curly braces in snippet.

site/docs/4.2/getting-started/javascript.md

@@ -50,7 +50,9 @@ All infinitive events provide [`preventDefault()`](https://developer.mozilla.org
 
 {% highlight js %}
 $('#myModal').on('show.bs.modal', function (e) {
-  if (!data) return e.preventDefault() // stops modal from being shown
+  if (!data) {
+    return e.preventDefault() // stops modal from being shown
+  }
 })
 {% endhighlight %}