Sample
Measure NaN and fractional fromIndex coercion in es-toolkit/compat findIndex at es-toolkit 1.50.0
sha256:2d9354edef7b8172f78ea6ba44242ec2c0fdbdf6117564ee919d50227f9a0b32
PUBLISHED
L3_CONTRACT_PASS
MIT-0
Execution evidence
Declared environment and signed verification runs are separated so you can see exactly what this sample proves.
Evidence basisSigned contract pass
Verification receipts1
Verification levelL3_CONTRACT_PASS
Declared environment
- Execution context
- node
- Operating system
- linux
- Architecture
- x64
- Runtime
- node
- Language
- node
- Package manager
- npm
Verification-run environments
- Execution context
- node 22
- Operating system
- linux alpine · musl
- Architecture
- x64
- Runtime
- node 22
- Language
- javascript
- Package manager
- npm
- Execution
- container · docker
CONTAINER_RUN · compile:SKIPPED · contract:PASS · load:PASS · resolve:PASS · node-typescript@1 · 2026-08-17
Case
- Goal
- Measure NaN and fractional fromIndex coercion in es-toolkit/compat findIndex at es-toolkit 1.50.0 HOW
- Packages
-
es-toolkit 1.50.0
- Environment
- node
- Created
- 2026-08-17T03:52:07Z
Commonly assumed
es-toolkit/compat findIndex passes a NaN or fractional fromIndex through as its return value when the predicate matches.
The sample's author recorded this as what a developer or model would expect here. The contract below is what actually ran.
Contract
- assert findIndex([1, 2], item => item === 1, NaN) returns 0
- assert findIndex([1, 2, 3], () => true, 1.9) returns 1
Files
- NOTES.md
- csx.json
- package-lock.json
- package.json
- test/contract.mjs
Download the source artifact (tar.gz)
Origin Seeder
csx-seed
Verification receipts
- node 22 · linux alpine/x64 · docker · CONTAINER_RUN · compile:SKIPPED · contract:PASS · load:PASS · resolve:PASS · node-typescript@1 · 2026-08-17 · ed25519:d91480838ac982c9