fix(shop): repair duplicated initialization block that left shop.js unparsable

[MOHITKOURAV01]

Closes #1696

What was wrong

frontend/scripts/shop.js did not parse. npm run check:syntax was red on main:

❌ 1 of 652 JavaScript file(s) failed to parse:
  frontend/scripts/shop.js:2499
      Unexpected end of input

The responsive-design refactor duplicated the initialization block at the bottom of the file and then interleaved the two copies. The tail ended up with two DOMContentLoaded registrations: the first with an arrow body that is never closed and a clear-filters listener that lost its body and picked up { rootMargin: "200px 0px" } — an IntersectionObserver options object belonging to observeSentinel() — as its third argument; the second re-doing the same element lookups, stopping halfway through them, and running into orphaned fragments of the first handler's body that referenced a filterUrlParams no longer in scope.

A SyntaxError aborts the whole script, so shop.html had no JavaScript: no product fetch, no filters, no sort, no infinite scroll, no search suggestions.

What this does

Collapses the two blocks back into the single handler the page has always needed, reconstructed from b8b934a^, and restores the clear-filters behaviour the merge stranded. That behaviour matters beyond tidiness: a shopper arriving from the mega menu carries category/subcategory in the query string, and filters.megaCategory / filters.megaSubcategory are seeded from them. Resetting only the checkboxes leaves both in place, so the next applyFilters() re-applies the filter the button just cleared and a reload brings it back. The handler now strips the params, rewrites the address bar, clears the mega filters, and re-runs the query.

Two small things kept from the reconstruction rather than the original:

• handleCategorySelect returns early when a card has no data-category, instead of building a checkbox with value="undefined".
• The stray addEventListener options object is gone. The browser silently accepts it — it reads as an options bag with no recognised keys — which is why this only ever looked like a listener that was wired and was not.

The call shape

The listener is written as the multi-line form:

document.addEventListener(
    "DOMContentLoaded",
    () => {
        ...
    }
);

not the compact document.addEventListener("DOMContentLoaded", () => { ... });. That is not a style preference — tests/mergeScarRegression.test.js already pins it:

it('closes that listener rather than running on into what follows', () => {
    // The #1444 scar itself: `}\n);` closes the arrow function and the call
    // it is an argument to. Dropping the `);` merged the listener into the
    // next declaration.
    expect(source.slice(listener)).toMatch(/\n\s*\}\n\s*\);/);
});

That suite has been red on main since the refactor. This makes its parses, has exactly one DOMContentLoaded initialiser and closes that listener cases green again.

Guard

backend/tests/frontendScriptParse.test.js compiles every file under frontend/scripts with vm.Script, the same parse goal a classic <script> tag and CommonJS use, retrying genuine ES modules the way scripts/check-syntax.js does. It then pins the shape of shop.js's init block: one DOMContentLoaded registration, one declaration of filterUrlParams with no stranded uses, no observer options handed to addEventListener, and all six steps of the clear-filters handler present.

check:syntax already catches the parse failure, but it is a separate CI step; having it in the jest suite puts the failure next to the behaviour it breaks.

Verification

$ npm run check:syntax
✅ syntax check passed — 652 JavaScript file(s) parsed cleanly

$ backend/node_modules/.bin/jest --rootDir backend tests/frontendScriptParse.test.js
Tests:       81 passed, 81 total

Confirmed the guard is real by stashing the shop.js fix and re-running the new test against the broken file:

✕ shop.js parses as a classic script
✕ exactly one DOMContentLoaded listener is registered
✕ no statement references an undeclared filterUrlParams
✕ addEventListener is never handed IntersectionObserver options
Tests:       4 failed, 77 passed, 81 total

The pre-existing tests/mergeScarRegression.test.js goes from three failures on main to one:

frontend/scripts/shop.js
  ✓ parses
  ✓ has exactly one DOMContentLoaded initialiser
  ✓ closes that listener rather than running on into what follows
  ✓ declares no function twice
  ✓ declares the functions its own code calls
  ✓ resolves the clear-filters button and sort select by the ids the page uses
  ✓ has one owner for the clear-filters click

The one it still reports — frontend/scripts/product-cards-home.js › declares the stock bindings its card template reads — is a different file and a separate defect from the same refactor, and is out of scope here.

Also ran check:assets, check:a11y, check:sitemap, check:boot and check:modules — all pass.

---

CI note

Syntax check ✅ and Server boots ✅ — the two jobs that were red on main because of this file.

Backend tests is still red, on suites this PR does not touch. All five already fail on main:

suite	failing case	fixed by
mergeScarRegression	product-cards-home.js › declares the stock bindings its card template reads	not yet — separate defect from the same refactor
cartBulkSelection	does not put handlers on the global object	not yet
wishlistReads	7 cases, all p.is_active = 1 missing from the queries	not yet
migrationViewColumns	no two migrations claim the same version	#1705
fraudMonitoringQueue	takes the next free migration number	#1705

This PR takes mergeScarRegression's frontend/scripts/shop.js block from three failures to zero:

frontend/scripts/shop.js
  ✓ parses
  ✓ has exactly one DOMContentLoaded initialiser
  ✓ closes that listener rather than running on into what follows
  ✓ declares no function twice
  ✓ declares the functions its own code calls
  ✓ resolves the clear-filters button and sort select by the ids the page uses
  ✓ has one owner for the clear-filters click

The Vercel check fails on every PR in this repository with "Authorization required to deploy" against the bhuvanshs-projects team, unrelated to any change.

[hydra-maintainer]

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[hydra-maintainer]

🔍 Quality Gate Report

✅ All quality gates passed!

Status	Check	Details
✅	Linked Issue	PR description references a closing issue ✅

[hydra-maintainer]

🤖 AI Code Review

🔴 Score: 50/100 | comment

AI review unavailable at this time.

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Automated AI review — a human maintainer will also review.

[hydra-maintainer]

💡 Suggested reviewers based on relevant file history: @Aditya8369, @Pcmhacker-hero

[hydra-maintainer]

🟡 PR Health Score: 55/100

This PR's health score is below the 75/100 threshold for a healthy label.

Status	Signal
✅	Test coverage
✅	Linked issue
✅	PR description (≥50 chars)
❌	DCO sign-off
⬜ 0 approval(s)	Approvals
❌	Diff size < 400 lines

Improving these signals will help reviewers engage faster and raise your score. 💪