# Behavior traces — trekhleb/javascript-algorithms

> Canonical page: https://codevetter.com/unpack/javascript-algorithms/behavior-traces

# Behavior traces — trekhleb/javascript-algorithms

Scanned commit 85293e3e2b88f4d2ce330d956b139cf628aa1e82 (2026-07-25). Generated by codevetter codevetter 1.12.0 on 2026-09-22.

Three flows were traced end-to-end. (1) Test execution: npm test -> jest -> testRegex match -> test file imports module under test -> assertions on return values/toString. (2) Sorting: QuickSort construction -> Sort.initSortingCallbacks -> sort() recursion driven by Comparator and visitingCallback. (3) BFS over a graph: callback init with seen-set -> Queue enqueue/dequeue -> getNeighbors -> allowTraversal gating. A fourth flow (seam carving) shows the only IO path: PNG load -> energy map -> DP seam -> in-place pixel shift.
- Test-run trace: `npm test` invokes jest, which applies testRegex '(/__tests__/.*|(\\.|/)(test|spec))\\.jsx?$' from jest.config.js, picks up files like src/data-structures/linked-list/__test__/LinkedList.test.js, which imports ../LinkedList, which imports LinkedListNode and ../../utils/comparator/Comparator. — [package.json#L32](https://github.com/trekhleb/javascript-algorithms/blob/85293e3e2b88f4d2ce330d956b139cf628aa1e82/package.json#L32) [jest.config.js#L22](https://github.com/trekhleb/javascript-algorithms/blob/85293e3e2b88f4d2ce330d956b139cf628aa1e82/jest.config.js#L22) [src/data-structures/linked-list/__test__/LinkedList.test.js#L1-6](https://github.com/trekhleb/javascript-algorithms/blob/85293e3e2b88f4d2ce330d956b139cf628aa1e82/src/data-structures/linked-list/__test__/LinkedList.test.js#L1-L6) [src/data-structures/linked-list/LinkedList.js#L1-2](https://github.com/trekhleb/javascript-algorithms/blob/85293e3e2b88f4d2ce330d956b139cf628aa1e82/src/data-structures/linked-list/LinkedList.js#L1-L2)
- Sorting trace (QuickSort): new QuickSort(callbacks) -> Sort constructor -> Sort.initSortingCallbacks fills visitingCallback stub and wraps compareCallback in Comparator -> sort(originalArray) clones array -> shift() pivot -> partition loop calls callbacks.visitingCallback and comparator.equal/lessThan -> recursive sort of left/right -> concat result. — [src/algorithms/sorting/Sort.js#L12-29](https://github.com/trekhleb/javascript-algorithms/blob/85293e3e2b88f4d2ce330d956b139cf628aa1e82/src/algorithms/sorting/Sort.js#L12-L29) [src/algorithms/sorting/quick-sort/QuickSort.js#L8-47](https://github.com/trekhleb/javascript-algorithms/blob/85293e3e2b88f4d2ce330d956b139cf628aa1e82/src/algorithms/sorting/quick-sort/QuickSort.js#L8-L47)
- BFS trace: breadthFirstSearch(graph, startVertex, callbacks) -> initCallbacks builds allowTraversal closure with `seen` map -> new Queue() -> enqueue(startVertex) -> while !isEmpty: dequeue -> enterVertex -> graph.getNeighbors(currentVertex) -> allowTraversal decides enqueue -> leaveVertex -> repeat. — [src/algorithms/graph/breadth-first-search/breadthFirstSearch.js#L19-74](https://github.com/trekhleb/javascript-algorithms/blob/85293e3e2b88f4d2ce330d956b139cf628aa1e82/src/algorithms/graph/breadth-first-search/breadthFirstSearch.js#L19-L74) [src/data-structures/queue/Queue.js#L36-48](https://github.com/trekhleb/javascript-algorithms/blob/85293e3e2b88f4d2ce330d956b139cf628aa1e82/src/data-structures/queue/Queue.js#L36-L48) [src/data-structures/graph/Graph.js#L39-41](https://github.com/trekhleb/javascript-algorithms/blob/85293e3e2b88f4d2ce330d956b139cf628aa1e82/src/data-structures/graph/Graph.js#L39-L41)
- DFS trace: depthFirstSearch -> initCallbacks (same seen-set pattern as BFS) -> depthFirstSearchRecursive -> enterVertex -> forEach neighbor -> allowTraversal gate -> recurse -> leaveVertex; recursion depth equals longest path, no explicit stack structure. — [src/algorithms/graph/depth-first-search/depthFirstSearch.js#L17-68](https://github.com/trekhleb/javascript-algorithms/blob/85293e3e2b88f4d2ce330d956b139cf628aa1e82/src/algorithms/graph/depth-first-search/depthFirstSearch.js#L17-L68)
- Seam-carving trace: test calls pngLoad (fs.createReadStream.pipe(new PNG()).on('parsed')) to build an ImageData-shaped object -> resizeImageWidth({img,toWidth}) -> per removed column: calculateEnergyMap (getPixelEnergy of left/middle/right RGB deltas) -> findLowEnergySeam (DP seamPixelsMap then backtrack via `previous` links) -> deleteSeam (row-wise setPixel left-shift) -> return {img, size}. — [src/algorithms/image-processing/seam-carving/__tests__/resizeImageWidth.node.js#L43-68](https://github.com/trekhleb/javascript-algorithms/blob/85293e3e2b88f4d2ce330d956b139cf628aa1e82/src/algorithms/image-processing/seam-carving/__tests__/resizeImageWidth.node.js#L43-L68) [src/algorithms/image-processing/seam-carving/resizeImageWidth.js#L92-251](https://github.com/trekhleb/javascript-algorithms/blob/85293e3e2b88f4d2ce330d956b139cf628aa1e82/src/algorithms/image-processing/seam-carving/resizeImageWidth.js#L92-L251) [src/algorithms/image-processing/utils/imageData.js](https://github.com/trekhleb/javascript-algorithms/blob/85293e3e2b88f4d2ce330d956b139cf628aa1e82/src/algorithms/image-processing/utils/imageData.js)
- HashTable write trace: set(key,value) -> hash(key) (charCode sum % buckets.length) -> this.keys[key]=keyHash -> bucket LinkedList.find({callback: nodeValue.key===key}) -> append new {key,value} node or overwrite node.value.value. — [src/data-structures/hash-table/HashTable.js#L27-64](https://github.com/trekhleb/javascript-algorithms/blob/85293e3e2b88f4d2ce330d956b139cf628aa1e82/src/data-structures/hash-table/HashTable.js#L27-L64) [src/data-structures/linked-list/LinkedList.js#L137-159](https://github.com/trekhleb/javascript-algorithms/blob/85293e3e2b88f4d2ce330d956b139cf628aa1e82/src/data-structures/linked-list/LinkedList.js#L137-L159)
- LinkedList deletion trace: delete(value) strips all matching head nodes in a while loop, then walks currentNode.next unlinking matches via compare.equal, finally reassigns this.tail if the tail matched — O(n) with the injected comparator deciding equality. — [src/data-structures/linked-list/LinkedList.js#L95-129](https://github.com/trekhleb/javascript-algorithms/blob/85293e3e2b88f4d2ce330d956b139cf628aa1e82/src/data-structures/linked-list/LinkedList.js#L95-L129)
- LRUCache.get trace: get(key) -> nodesMap lookup -> promote(node) which evicts then re-appends the node to the tail of the doubly-linked list -> return node.val; set() appends a new node and evicts head.next when size exceeds capacity. — [src/data-structures/lru-cache/LRUCache.js#L50-150](https://github.com/trekhleb/javascript-algorithms/blob/85293e3e2b88f4d2ce330d956b139cf628aa1e82/src/data-structures/lru-cache/LRUCache.js#L50-L150)
- CI pipeline trace: push/PR to master -> actions/checkout@v4 -> setup-node 22.x -> npm i -> npm run lint (eslint ./src/**) -> npm run coverage (jest --coverage, enforcing 100/95/100/100 thresholds) -> codecov upload. — [.github/workflows/CI.yml#L16-35](https://github.com/trekhleb/javascript-algorithms/blob/85293e3e2b88f4d2ce330d956b139cf628aa1e82/.github/workflows/CI.yml#L16-L35) [jest.config.js#L32-39](https://github.com/trekhleb/javascript-algorithms/blob/85293e3e2b88f4d2ce330d956b139cf628aa1e82/jest.config.js#L32-L39) [package.json#L30-34](https://github.com/trekhleb/javascript-algorithms/blob/85293e3e2b88f4d2ce330d956b139cf628aa1e82/package.json#L30-L34)

Every claim links to its cited files at the pinned commit. Citations identify source evidence; they do not establish runtime correctness. Independent CodeVetter scan — not reviewed by upstream maintainers.

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