fix: enable focus-visible in Firefox 90 (#2075)

src/routes/_utils/supportsFocusVisible.js

@@ -1,8 +1,8 @@
 import { thunk } from './thunk.js'
 import { supportsSelector } from './supportsSelector.js'
-import { isFirefox } from './userAgent/isFirefox.js'
+import { isFirefoxPre90 } from './userAgent/isFirefoxPre90.js'
 
-// Disabling for now in Firefox due to bugs:
+// Disabling in Firefox <90 due to bugs:
 // https://bugzilla.mozilla.org/show_bug.cgi?id=1699154
 // https://bugzilla.mozilla.org/show_bug.cgi?id=1711057
-export const supportsFocusVisible = thunk(() => (!isFirefox() && supportsSelector(':focus-visible')))
+export const supportsFocusVisible = thunk(() => (!isFirefoxPre90() && supportsSelector(':focus-visible')))

src/routes/_utils/userAgent/isFirefox.js

@@ -1,5 +0,0 @@
-import { thunk } from '../thunk.js'
-
-export const isFirefox = thunk(() => {
-  return process.browser && typeof InstallTrigger !== 'undefined' // https://stackoverflow.com/a/9851769/680742
-})

src/routes/_utils/userAgent/isFirefoxPre90.js

@@ -0,0 +1,9 @@
+import { thunk } from '../thunk.js'
+
+export const isFirefoxPre90 = thunk(() => {
+  return process.browser &&
+    // https://stackoverflow.com/a/9851769/680742
+    typeof InstallTrigger !== 'undefined' &&
+    // https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/at#browser_compatibility
+    !Array.prototype.at
+})