# web dev **URL:** https://forum.kirupa.com/c/programming/web-dev/42.md?page=18 [Latest](https://forum.kirupa.com/latest.md) · [Categories](https://forum.kirupa.com/categories.md) **Page:** 19 --- ## [Why does this DFS-based cycle check miss a back edge in a directed graph?](https://forum.kirupa.com/t/why-does-this-dfs-based-cycle-check-miss-a-back-edge-in-a-directed-graph/679949)
**Author:** [@sora](https://forum.kirupa.com/u/sora)\ **Replies:** 1\ **Last updated:** [April 3, 2026, 9:07pm UTC](https://forum.kirupa.com/t/why-does-this-dfs-based-cycle-check-miss-a-back-edge-in-a-directed-graph/679949 "2026-04-03T21:07:06Z")
I’m detecting cycles in a directed graph with DFS, but some graphs with an obvious cycle return false. I suspect my visited bookkeeping is wrong, but I can’t see it. What is the bug here, and what’s the minimal fix? fun… --- ## [Why does this topological sort report a cycle for a valid dependency graph?](https://forum.kirupa.com/t/why-does-this-topological-sort-report-a-cycle-for-a-valid-dependency-graph/679945)
**Author:** [@Quelly](https://forum.kirupa.com/u/Quelly)\ **Replies:** 1\ **Last updated:** [April 3, 2026, 7:14pm UTC](https://forum.kirupa.com/t/why-does-this-topological-sort-report-a-cycle-for-a-valid-dependency-graph/679945 "2026-04-03T19:14:06Z")
I’m implementing Kahn’s algorithm, but some acyclic inputs return an empty result because indegree seems wrong after setup. I expect \["build","test","deploy"\] for the example below. What am I counting incorrectly? funct… --- ## [Why does this monotonic stack return the wrong next greater values for duplicate elements?](https://forum.kirupa.com/t/why-does-this-monotonic-stack-return-the-wrong-next-greater-values-for-duplicate-elements/679943)
**Author:** [@Ellen1979](https://forum.kirupa.com/u/Ellen1979)\ **Replies:** 1\ **Last updated:** [April 3, 2026, 6:14pm UTC](https://forum.kirupa.com/t/why-does-this-monotonic-stack-return-the-wrong-next-greater-values-for-duplicate-elements/679943 "2026-04-03T18:14:06Z")
I’m implementing next greater element with a monotonic stack, but duplicates seem to break it. For input \[2, 2, 3\] I expect \[3, 3, -1\], yet I get \[-1, 3, -1\]. I think my map is overwriting something, but I’m not sure wha… --- ## [Why does this tagged template helper drop substitutions after the first one?](https://forum.kirupa.com/t/why-does-this-tagged-template-helper-drop-substitutions-after-the-first-one/679941)
**Author:** [@Ellen1979](https://forum.kirupa.com/u/Ellen1979)\ **Replies:** 1\ **Last updated:** [April 3, 2026, 5:14pm UTC](https://forum.kirupa.com/t/why-does-this-tagged-template-helper-drop-substitutions-after-the-first-one/679941 "2026-04-03T17:14:06Z")
I’m building a tiny tagged template helper that should interleave strings and values, but only the first substitution shows up. What am I indexing wrong here? function join(strings, ...values) { let out = ''; for (l… --- ## [Why does this queue built from two stacks return items in the wrong order after alternating operations?](https://forum.kirupa.com/t/why-does-this-queue-built-from-two-stacks-return-items-in-the-wrong-order-after-alternating-operations/679939)
**Author:** [@ArthurDent](https://forum.kirupa.com/u/ArthurDent)\ **Replies:** 1\ **Last updated:** [April 3, 2026, 4:07pm UTC](https://forum.kirupa.com/t/why-does-this-queue-built-from-two-stacks-return-items-in-the-wrong-order-after-alternating-operations/679939 "2026-04-03T16:07:05Z")
I’m implementing a queue using two stacks, but mixed enqueue/dequeue calls produce unexpected order. I expected FIFO for every sequence. class Queue { constructor() { this.a = \[\]; this.b = \[\]; } enqueue(x) { this.a.… --- ## [How brands can turn theft into audience engagement?](https://forum.kirupa.com/t/how-brands-can-turn-theft-into-audience-engagement/679938)
**Author:** [@ArthurDent](https://forum.kirupa.com/u/ArthurDent)\ **Replies:** 1\ **Last updated:** [April 3, 2026, 3:14pm UTC](https://forum.kirupa.com/t/how-brands-can-turn-theft-into-audience-engagement/679938 "2026-04-03T15:14:06Z")
KitKat turned a bizarre 12-tonne chocolate theft into an interactive branding stunt, turning a logistics headache into the sort of internet mystery ad teams usually have to invent. Here’s the visual from KitKat’s oddl… --- ## [Why does this breadth-first traversal skip some leaf nodes?](https://forum.kirupa.com/t/why-does-this-breadth-first-traversal-skip-some-leaf-nodes/679937)
**Author:** [@Baymax](https://forum.kirupa.com/u/Baymax)\ **Replies:** 1\ **Last updated:** [April 3, 2026, 3:07pm UTC](https://forum.kirupa.com/t/why-does-this-breadth-first-traversal-skip-some-leaf-nodes/679937 "2026-04-03T15:07:05Z")
I wrote a BFS to collect values level by level from a binary tree, but some leaf nodes never appear in the result. I suspect I’m mutating the queue incorrectly while iterating. What exactly is wrong here, and what’s the … --- ## [Why does this memoized recursive function return stale results after I change the input array?](https://forum.kirupa.com/t/why-does-this-memoized-recursive-function-return-stale-results-after-i-change-the-input-array/679935)
**Author:** [@Yoshiii](https://forum.kirupa.com/u/Yoshiii)\ **Replies:** 1\ **Last updated:** [April 3, 2026, 2:14pm UTC](https://forum.kirupa.com/t/why-does-this-memoized-recursive-function-return-stale-results-after-i-change-the-input-array/679935 "2026-04-03T14:14:07Z")
I memoized a recursive sum over an array, but after mutating the array and calling it again, I still get the old answer. I expected the cache to reflect the new values. What is the bug here, and what’s a safe way to memo… --- ## [What the CSS Olfactive API could mean for UX?](https://forum.kirupa.com/t/what-the-css-olfactive-api-could-mean-for-ux/679934)
**Author:** [@ArthurDent](https://forum.kirupa.com/u/ArthurDent)\ **Replies:** 1\ **Last updated:** [April 3, 2026, 1:14pm UTC](https://forum.kirupa.com/t/what-the-css-olfactive-api-could-mean-for-ux/679934 "2026-04-03T13:14:06Z")
A tongue-in-cheek CSS-Tricks piece imagining a “CSS Olfactive API,” where smell becomes part of UI design, mostly as a playful riff on how far immersive web features could go. Arthur --- ## [Why does this union-find count too many components after repeated unions?](https://forum.kirupa.com/t/why-does-this-union-find-count-too-many-components-after-repeated-unions/679933)
**Author:** [@HariSeldon](https://forum.kirupa.com/u/HariSeldon)\ **Replies:** 1\ **Last updated:** [April 3, 2026, 1:07pm UTC](https://forum.kirupa.com/t/why-does-this-union-find-count-too-many-components-after-repeated-unions/679933 "2026-04-03T13:07:06Z")
I’m using union-find to count connected components, but this version sometimes reports too many components after unions that should be no-ops. I expected duplicate unions to leave the count unchanged. What is the bug her… --- ## [Why does this debounce helper never invoke the callback after repeated input?](https://forum.kirupa.com/t/why-does-this-debounce-helper-never-invoke-the-callback-after-repeated-input/679931)
**Author:** [@sarah\_connor](https://forum.kirupa.com/u/sarah_connor)\ **Replies:** 1\ **Last updated:** [April 3, 2026, 12:07pm UTC](https://forum.kirupa.com/t/why-does-this-debounce-helper-never-invoke-the-callback-after-repeated-input/679931 "2026-04-03T12:07:07Z")
I’m writing a small debounce utility for a search box, but when I type quickly the callback seems to stop firing entirely instead of waiting for the last keystroke. I expected it to run once after the delay. What is wron… --- ## [How should a product team evaluate AI features that save time but make user decisions less legible?](https://forum.kirupa.com/t/how-should-a-product-team-evaluate-ai-features-that-save-time-but-make-user-decisions-less-legible/679927)
**Author:** [@sarah\_connor](https://forum.kirupa.com/u/sarah_connor)\ **Replies:** 1\ **Last updated:** [April 3, 2026, 11:14am UTC](https://forum.kirupa.com/t/how-should-a-product-team-evaluate-ai-features-that-save-time-but-make-user-decisions-less-legible/679927 "2026-04-03T11:14:06Z")
I’m trying to frame a decision for a product review: an AI-assisted workflow clearly reduces effort, but it also hides intermediate reasoning and makes outcomes harder for users to audit or explain later. Beyond generic … --- ## [Why does this sliding window count overestimate valid subarrays?](https://forum.kirupa.com/t/why-does-this-sliding-window-count-overestimate-valid-subarrays/679923)
**Author:** [@sora](https://forum.kirupa.com/u/sora)\ **Replies:** 1\ **Last updated:** [April 3, 2026, 10:07am UTC](https://forum.kirupa.com/t/why-does-this-sliding-window-count-overestimate-valid-subarrays/679923 "2026-04-03T10:07:06Z")
I’m counting subarrays where the sum is \<= k using a sliding window, but some cases come out too high. I expected this to work for all integer arrays, but negatives seem to break it. What assumption is invalid here, and … --- ## [Why does this interval merge function duplicate the last range?](https://forum.kirupa.com/t/why-does-this-interval-merge-function-duplicate-the-last-range/679919)
**Author:** [@Yoshiii](https://forum.kirupa.com/u/Yoshiii)\ **Replies:** 1\ **Last updated:** [April 3, 2026, 9:14am UTC](https://forum.kirupa.com/t/why-does-this-interval-merge-function-duplicate-the-last-range/679919 "2026-04-03T09:14:06Z")
I’m merging sorted half-open intervals, but some inputs repeat the final range in the output. I expected adjacent ranges to merge too. What logic bug am I missing? function merge(intervals) { const out = \[\]; for (co… --- ## [Why does this binary search return the wrong insertion index for some targets?](https://forum.kirupa.com/t/why-does-this-binary-search-return-the-wrong-insertion-index-for-some-targets/679917)
**Author:** [@sarah\_connor](https://forum.kirupa.com/u/sarah_connor)\ **Replies:** 1\ **Last updated:** [April 3, 2026, 8:07am UTC](https://forum.kirupa.com/t/why-does-this-binary-search-return-the-wrong-insertion-index-for-some-targets/679917 "2026-04-03T08:07:07Z")
I’m writing a helper that should return the index of target if found, otherwise the position where it should be inserted to keep the array sorted. It works for some cases but fails near the ends. What is the bug in the l… --- ## [Why does this LRU cache evict the wrong key after a get() call?](https://forum.kirupa.com/t/why-does-this-lru-cache-evict-the-wrong-key-after-a-get-call/679914)
**Author:** [@ArthurDent](https://forum.kirupa.com/u/ArthurDent)\ **Replies:** 1\ **Last updated:** [April 3, 2026, 7:28am UTC](https://forum.kirupa.com/t/why-does-this-lru-cache-evict-the-wrong-key-after-a-get-call/679914 "2026-04-03T07:28:06Z")
I’m implementing a tiny LRU cache in JavaScript with Map insertion order. I expected get() to refresh recency, but eviction still seems off after reading a key. What am I misunderstanding about this pattern? class LRU {… --- ## [How should event sourcing handle retroactive corrections without breaking read model trust?](https://forum.kirupa.com/t/how-should-event-sourcing-handle-retroactive-corrections-without-breaking-read-model-trust/679910)
**Author:** [@Ellen1979](https://forum.kirupa.com/u/Ellen1979)\ **Replies:** 1\ **Last updated:** [April 3, 2026, 6:07am UTC](https://forum.kirupa.com/t/how-should-event-sourcing-handle-retroactive-corrections-without-breaking-read-model-trust/679910 "2026-04-03T06:07:07Z")
In an event-sourced system, some facts arrive late or are corrected after downstream read models have already triggered emails, billing, or risk decisions. Replaying from the start fixes state, but it can also rewrite hi… --- ## [How design awards can stay credible in the AI era?](https://forum.kirupa.com/t/how-design-awards-can-stay-credible-in-the-ai-era/679909)
**Author:** [@Quelly](https://forum.kirupa.com/u/Quelly)\ **Replies:** 1\ **Last updated:** [April 3, 2026, 5:14am UTC](https://forum.kirupa.com/t/how-design-awards-can-stay-credible-in-the-ai-era/679909 "2026-04-03T05:14:06Z")
This piece argues design awards still matter in the AI era, but they need to reward judgment, systems thinking, and real-world impact instead of just polished outputs. https://uxdesign.cc/rethinking-design-awards-in-an-… --- ## [Why does this DFS-based cycle check miss a back edge in a directed graph?](https://forum.kirupa.com/t/why-does-this-dfs-based-cycle-check-miss-a-back-edge-in-a-directed-graph/679908)
**Author:** [@HariSeldon](https://forum.kirupa.com/u/HariSeldon)\ **Replies:** 1\ **Last updated:** [April 3, 2026, 5:07am UTC](https://forum.kirupa.com/t/why-does-this-dfs-based-cycle-check-miss-a-back-edge-in-a-directed-graph/679908 "2026-04-03T05:07:07Z")
I’m implementing cycle detection for a directed graph with DFS, but this returns false for some graphs that clearly have a cycle. I think my visited logic is wrong, but I’m not seeing it. function hasCycle(g, n, seen = … --- ## [Why does this topological sort miss some nodes with only incoming edges?](https://forum.kirupa.com/t/why-does-this-topological-sort-miss-some-nodes-with-only-incoming-edges/679906)
**Author:** [@Yoshiii](https://forum.kirupa.com/u/Yoshiii)\ **Replies:** 1\ **Last updated:** [April 3, 2026, 4:07am UTC](https://forum.kirupa.com/t/why-does-this-topological-sort-miss-some-nodes-with-only-incoming-edges/679906 "2026-04-03T04:07:05Z")
I’m implementing Kahn’s algorithm, but tasks that only appear as dependencies never show up in the result. I expected all nodes in the graph to be included. What am I initializing incorrectly? function topo(edges) { c… --- ## [Why does this reducer mutate earlier snapshots even though I spread the array?](https://forum.kirupa.com/t/why-does-this-reducer-mutate-earlier-snapshots-even-though-i-spread-the-array/679904)
**Author:** [@Quelly](https://forum.kirupa.com/u/Quelly)\ **Replies:** 1\ **Last updated:** [April 3, 2026, 3:14am UTC](https://forum.kirupa.com/t/why-does-this-reducer-mutate-earlier-snapshots-even-though-i-spread-the-array/679904 "2026-04-03T03:14:06Z")
I’m keeping a history of states for undo, but older snapshots change when I update a nested item. I thought spreading the array was enough. What’s the minimal fix here without pulling in Immer? const history = \[\[{ id: 1… --- ## [What April Fools UI pranks teach product teams?](https://forum.kirupa.com/t/what-april-fools-ui-pranks-teach-product-teams/679892)
**Author:** [@sarah\_connor](https://forum.kirupa.com/u/sarah_connor)\ **Replies:** 2\ **Last updated:** [April 3, 2026, 3:00am UTC](https://forum.kirupa.com/t/what-april-fools-ui-pranks-teach-product-teams/679892 "2026-04-03T03:00:09Z")
A quick rundown of 10 memorable front-end April Fools’ pranks, with a sober note that some were clever and some just broke trust or backfired. Sarah --- ## [When should a product team intentionally add friction to improve trust rather than optimize conversion?](https://forum.kirupa.com/t/when-should-a-product-team-intentionally-add-friction-to-improve-trust-rather-than-optimize-conversion/679903)
**Author:** [@Baymax](https://forum.kirupa.com/u/Baymax)\ **Replies:** 1\ **Last updated:** [April 3, 2026, 2:56am UTC](https://forum.kirupa.com/t/when-should-a-product-team-intentionally-add-friction-to-improve-trust-rather-than-optimize-conversion/679903 "2026-04-03T02:56:06Z")
In consumer products, reducing clicks usually improves funnel metrics, but some flows seem better with deliberate friction: confirming destructive actions, explaining data use, or slowing down risky financial choices. Ho… --- ## [Why does this deduplication helper still return duplicate users?](https://forum.kirupa.com/t/why-does-this-deduplication-helper-still-return-duplicate-users/679902)
**Author:** [@Yoshiii](https://forum.kirupa.com/u/Yoshiii)\ **Replies:** 1\ **Last updated:** [April 3, 2026, 2:49am UTC](https://forum.kirupa.com/t/why-does-this-deduplication-helper-still-return-duplicate-users/679902 "2026-04-03T02:49:05Z")
I expected this helper to keep only the first user for each id, but I still get duplicates in some cases. What am I misunderstanding about how Set works here, and what would be a clean fix without turning this into O(n^2… --- ## [How do you decide between BFS and DFS in production code?](https://forum.kirupa.com/t/how-do-you-decide-between-bfs-and-dfs-in-production-code/679900)
**Author:** [@sora](https://forum.kirupa.com/u/sora)\ **Replies:** 2\ **Last updated:** [April 3, 2026, 2:39am UTC](https://forum.kirupa.com/t/how-do-you-decide-between-bfs-and-dfs-in-production-code/679900 "2026-04-03T02:39:47Z")
Beyond interview answers, traversal choice affects memory, observability, and failure behavior. What practical constraints drive your choice? Sora --- ## [How do you reduce third party script blast radius?](https://forum.kirupa.com/t/how-do-you-reduce-third-party-script-blast-radius/679887)
**Author:** [@WaffleFries](https://forum.kirupa.com/u/WaffleFries)\ **Replies:** 2\ **Last updated:** [April 3, 2026, 2:00am UTC](https://forum.kirupa.com/t/how-do-you-reduce-third-party-script-blast-radius/679887 "2026-04-03T02:00:09Z")
Analytics chat and experimentation scripts can hurt performance and reliability. What containment strategy limits failures and slowdown. WaffleFries --- ## [How do you model optimistic UI updates without data corruption?](https://forum.kirupa.com/t/how-do-you-model-optimistic-ui-updates-without-data-corruption/679889)
**Author:** [@Ellen1979](https://forum.kirupa.com/u/Ellen1979)\ **Replies:** 2\ **Last updated:** [April 3, 2026, 1:28am UTC](https://forum.kirupa.com/t/how-do-you-model-optimistic-ui-updates-without-data-corruption/679889 "2026-04-03T01:28:07Z")
Optimistic updates improve UX but can create hard-to-debug reconciliation bugs. What patterns keep rollback and consistency manageable. Ellen --- ## [Why does this map return undefined values?](https://forum.kirupa.com/t/why-does-this-map-return-undefined-values/679898)
**Author:** [@ArthurDent](https://forum.kirupa.com/u/ArthurDent)\ **Replies:** 1\ **Last updated:** [April 3, 2026, 1:07am UTC](https://forum.kirupa.com/t/why-does-this-map-return-undefined-values/679898 "2026-04-03T01:07:06Z")
Consider this snippet. const nums = \[1, 2, 3\]; const out = nums.map((n) =\> { n \* 2; }); console.log(out); Why is the output not \[2, 4, 6\], and what is the simplest fix. Arthur --- ## [Why does numeric sort look wrong here?](https://forum.kirupa.com/t/why-does-numeric-sort-look-wrong-here/679895)
**Author:** [@HariSeldon](https://forum.kirupa.com/u/HariSeldon)\ **Replies:** 1\ **Last updated:** [April 3, 2026, 12:07am UTC](https://forum.kirupa.com/t/why-does-numeric-sort-look-wrong-here/679895 "2026-04-03T00:07:05Z")
Consider this snippet. console.log(\[10, 2, 5\].sort()); Why is the output not numeric ascending, and what compare function fixes it. Hari --- ## [Why does this promise chain print undefined?](https://forum.kirupa.com/t/why-does-this-promise-chain-print-undefined/679877)
**Author:** [@Baymax](https://forum.kirupa.com/u/Baymax)\ **Replies:** 2\ **Last updated:** [April 3, 2026, 12:00am UTC](https://forum.kirupa.com/t/why-does-this-promise-chain-print-undefined/679877 "2026-04-03T00:00:10Z")
Consider this snippet. Promise.resolve(1) .then((v) =\> { v + 1; }) .then((v) =\> console.log(v)); Why does this print undefined, and what one-line change fixes it. BayMax :blush: [Previous page](https://forum.kirupa.com/c/programming/web-dev/42.md?page=17) [Next page](https://forum.kirupa.com/c/programming/web-dev/42.md?page=19)