[jjroelofs]

Summary

• Modernise js/rl-sorting-tracking.js to pass ESLint with @antfu/eslint-config (zero errors)
• Convert all var declarations to const/let
• Use arrow functions, object shorthand methods, template literals, and trailing commas
• Destructure viewSettings to pull only the three properties actually used (removes the unused entityIds assignment)
• Hoist storageKey out of the links.forEach loop since it depends only on experimentId, not the individual link
• Convert sendBatchedTurns from a hoisted function declaration to a const arrow for consistency with the rest of the file
• Remove trailing whitespace; add missing trailing newline
• No functional changes

Closes #4

Test plan

• Run npx eslint . and confirm zero errors
• Verify RL Sorting impression tracking still fires (IntersectionObserver batched turns via sendBeacon)
• Verify click reward tracking still fires (sessionStorage dedup, sendBeacon to RL endpoint)
• Confirm no regressions in Views pages with RL Sorting enabled

[jjroelofs]

Reviewed the full diff against the old file; no behavioral changes found. Looks good.

What I verified:

• The destructuring of settings.rlSorting.views[viewDisplayKey] correctly drops only entityIds, which was assigned but never read in the old code. The three properties that are used (experimentId, entityUrlMap, rlEndpointUrl) all survive, and the !experimentId || !rlEndpointUrl guard still runs after it.
• Hoisting storageKey out of the links.forEach loop is correct: it depends only on experimentId, which is fixed per view, so computing it once is equivalent and the click handlers close over the same value.
• Converting sendBatchedTurns from a hoisted function declaration to a const arrow is safe here because its only call sites (the setTimeout inside the IntersectionObserver callback) execute after the declaration; there is no temporal dead zone hazard.
• visibleArms and batchTimer correctly stay let since both are reassigned.

On CI: eslint, drupal-check, changes and emdash-lint are green. The drupal-lint failure is unrelated to this PR; the job dies during setup because composer cannot install phpcompatibility/php-compatibility (it reverts composer.json and exits before any linting runs). That is a CI infrastructure issue that will hit every PR in this repo until the lint action's dependency resolution is fixed.