Remove dead browser-support JS, fix a matchMedia support-detect bug - #1139
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Everything here is unconditionally true for Firefox ESR, Safari 15.6+, and evergreen browsers, so the feature-query gates and legacy prefixes around it are dead weight. - Unwrapped @supports (position: sticky) in _navigation.scss and @supports (display: flex) in _menu.scss. The menu.scss case merges align-items/display: flex directly into the existing .mzp-c-menu-title rule, replacing its display: block fallback outright rather than keeping a separate feature-query block for a feature every supported browser has. - Removed the base/elements/_reset.scss block resetting article, aside, details, figcaption, figure, footer, header, hgroup, main, nav, section, and summary to display: block -- every one of these has had correct default display in every supported browser for over a decade. Left the audio/video/canvas -> inline-block reset alone: that's a deliberate style choice (those are inline-level by spec in every browser), not a legacy-browser shim, so it doesn't belong to this cleanup. - Removed the &::-ms-expand selector in the Select form reset (pure legacy IE/Edge, matches nothing in any supported browser). - Replaced -webkit-appearance with the standard unprefixed appearance property in the two remaining form resets (search decoration, file upload button) and removed their now-unnecessary stylelint-disable comments. Re-enabled property-no-vendor-prefix and value-no-vendor-prefix in .stylelintrc.json as the ongoing enforcement lever -- confirmed empirically these two were the only real hits; the rules don't flag vendor-prefixed pseudo-elements (::-moz-focus-inner, ::-webkit-details-marker) or non-standard, prefix-only properties (-moz-osx-font-smoothing, -webkit-font-smoothing) that have no unprefixed equivalent, so the other 6 remaining prefixes in the codebase are correctly left alone. - appearance: button was flagged separately as a deprecated keyword for the unprefixed property (declaration-property-value-keyword-no-deprecated); changed to appearance: auto, which is the correct modern equivalent (native appearance for that pseudo-element is already button-shaped). - Removed stale "in IE"/"in Edge and IE" references from three comment blocks in _forms.scss. Left the normalize.css resets those comments document in place -- e.g. the textarea scrollbar and legend box-sizing resets -- since I can't confirm from source alone that every supported browser makes them fully redundant, and that's a bigger, separate call from removing definitively dead code like the @supports/-ms-/reset.scss cases above. Stacked on #1135 (v23/support-config). Part of #1084. Verified: npm run lint, npm test (47 specs, Firefox + Chrome), and a direct sass --verbose compile confirming the merged menu-title rule, the unwrapped sticky-nav rule, and the removed -ms-/@supports code in the compiled CSS.
…1084) - Removed the Element.matches() IE8 polyfill from utils.js entirely. Native Element.prototype.matches is supported in every browser in the new matrix; nextUntil() already calls el.matches() directly so nothing downstream changes. - Collapsed the addEventListener-else-addListener MediaQueryList fallback in navigation.js, menu.js, and footer.js down to a plain addEventListener call. The standard MediaQueryList.addEventListener has been supported since Safari 14 / Firefox 55 / Chrome 55 -- fully covered by the new matrix -- so the legacy addListener branch never runs in any supported browser. - Bug fix: MzpSupports.matchMedia required window.matchMedia('all').addListener -- the *deprecated* legacy MediaQueryList API -- to consider matchMedia supported. Any browser that removes the deprecated addListener while keeping standard matchMedia (as browsers increasingly do) would make this detect return false, silently disabling sticky navigation and everything else gated on window.MzpSupports.matchMedia (menu.js, footer.js). Fixed to check only for matchMedia itself. - Simplified two IE9 classList-polyfill workarounds in menu.js (removing classes one-at-a-time "in the correct order" per mozilla/bedrock#6221) to a single classList.remove('a', 'b') call -- multi-argument remove() is reliable in every supported browser now that the IE9 bug it worked around is out of scope. Left MzpSupports' public API (matchMedia, requestAnimationFrame, cssFeatureQueries, classList, details, intersectionObserver) and its consumers' gate checks in place per the v23 plan -- it's a documented UMD entry point (webpack.entrypoints.js) referenced in components/details-component/readme.md, so removing it outright is a separate, bigger breaking-API decision than this cleanup. All six detects are now unconditionally true for the supported matrix, which is effectively dead code, but keeping the module intact avoids a second breaking change bundled into this one. Didn't add a spec for the matchMedia fix -- supports.js computes each property once at module-import time via an IIFE, which doesn't fit this test harness's plain Jasmine-in-real-browser setup without module-mocking machinery this repo doesn't have. The existing menu.js/navigation.js/footer.js specs already exercise the changed addEventListener lines in real Firefox and Chrome (not jsdom), which is the practical coverage available here. Stacked on v23/support-css (browser-support CSS cleanup). Part of #1084. Verified: npm run lint, npm test (47 specs, Firefox + Chrome), and npm run build-package all pass.
stephaniehobson
added this pull request to stack #1146
September 11, 2026 17:21
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Description
Removes JS that's dead weight under the new browser support matrix (#1084), and fixes a real bug found along the way.
Element.matches()IE8 polyfill fromutils.jsentirely.addEventListener-else-addListenerMediaQueryListfallback innavigation.js,menu.js, andfooter.jsdown to a plainaddEventListenercall.MzpSupports.matchMediarequiredwindow.matchMedia('all').addListener— the deprecated legacyMediaQueryListAPI — to considermatchMediasupported. Any browser that removes the deprecated method while keeping standardmatchMediawould make this detect returnfalse, silently disabling sticky navigation and everything else gated on it. Fixed to check only formatchMediaitself.classList-polyfill workarounds inmenu.jsto a singleclassList.remove('a', 'b')call.MzpSupports's public API is left intact — it's a documented UMD entry point, so removing it is a separate, bigger breaking-API decision than this cleanup.CHANGELOG.md.Issue
Part of #1084
Testing
npm run lint,npm test(47 specs, Firefox + Chrome),npm run build-packageall pass.