Find the position of a matching item.
JavaScript: findIndex returns -1 when the predicate matches nothing.
console.log(["Ada", "Grace", "Linus"].findIndex(name => name === "Grace"));Expected output EXAMPLE
1
Details
Save as snippet.js and run node snippet.js. Uses built-in Node.js and JavaScript APIs. findIndex returns -1 when the predicate matches nothing.
Tested on Ubuntu 24.04.5 LTS · · v18.19.1 · nodejs 18.19.1+dfsg-6ubuntu5
Test inputs, results and environment
The exact published code ran in a dedicated Linux test container with prepared inputs. Unprivileged snippet process, external networking disabled, read-only root filesystem, and a fresh temporary working directory. Fixtures and output records are isolated from the application database. Testing covers this example and its stated checks, not every input, operating system, or runtime version. The Linux container shares its host's kernel; this is not a native Windows test.
- Architecture / host kernel
- x86_64 / 6.18.54.1-microsoft-standard-WSL2
- Snippet identity / locale
- uid=65534, gid=65534 (unprivileged) / C.UTF-8
- Interpreter invocation
node snippet.js- Container image ID
sha256:32dc2d998158b6554c99b73b533f423696a0f3e31e8cbea9db10b5eee9a2fadd- Code SHA-256
60a8614e02c03ad602a65c9795e00febf291026d60c85484bcb8edd227120703- Dependencies
- nodejs 18.19.1+dfsg-6ubuntu5
Test input setup
These are the prepared inputs used by the test harness. See Details above for the prerequisites and how to run this example.
# No input files required.
Observed standard output
1
Exit code: 0. Standard error: empty. Validation: Exact stdout comparison. System-dependent values above are one recorded run.