fix(react-virtualizer): prevent RangeError when numItems decreases while scrolled near bottom#616
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dmytrokirpa merged 3 commits intomicrosoft:mainfrom Mar 3, 2026
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…ile scrolled near bottom When filtering reduces numItems while actualIndex still holds a high scroll position, renderChildRows computed a negative arrayLength causing "RangeError: Invalid array length". Clamp arrayLength to zero with Math.max(0, ...) mirroring the guard already present in updateChildArray. Also guard calculateBefore against returning a negative buffer height when numItems is 0 (static sizing path). Fixes microsoft#607 Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
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mainframev
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Summary
Fixes #607 (in microsoft/fluentui-contrib)
renderChildRows: wrapnumItems - newIndexwithMath.max(0, ...)to prevent a negativearrayLengthfrom being passed tonew Array(), which threwRangeError: Invalid array lengthwhennumItemsdecreased (e.g. filtering) whileactualIndexwas still at a high scroll position.calculateBefore: wrapMath.min(actualIndex, numItems - 1)withMath.max(0, ...)to prevent a negativebeforeBufferHeightfor static-sized lists whennumItemsdrops to0.Both fixes mirror the guard already present in
updateChildArray(Math.max(0, numItems - startIndex)).Test plan
"should not crash with RangeError when numItems decreases while scrolled near the bottom"— simulatescontextIndex = 90withnumItemsfiltered from 100 → 10, asserts noRangeErroris thrown andvirtualizedChildren.length >= 0.useVirtualizerunit tests pass (yarn jest useVirtualizer.test).🤖 Generated with Claude Code