Count words using a Map.
Update a keyed counter without losing its value type.
const counts = new Map<string, number>();
for (const word of ["red", "blue", "red"]) {
counts.set(word, (counts.get(word) ?? 0) + 1);
}
console.log(counts.get("red"));Expected output EXAMPLE
2
Details
Requires TypeScript and Node.js. Save as snippet.ts, compile with tsc --strict --target ES2022 --module commonjs snippet.ts, then run node snippet.js. Map.get can return undefined, so the counter supplies an initial zero.
Tested on Ubuntu 24.04.5 LTS · · TypeScript 5.9.3; Node.js 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. Snippet process uid 65534 with a read-only root filesystem and temporary working files. Networking disabled. 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 process) / C.UTF-8
- Interpreter invocation
tsc --strict --target ES2022 --module commonjs snippet.ts && node snippet.js- Container image ID
sha256:ec91410a8f6ec3e985830b5e3a0560306d36f8c1c5ccd91a6699abe707123fa3- Code SHA-256
7c18af09dfc3db26e44292063edee902f283d412b4e0fb0986cdce8c3691dd55- 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
2
Exit code: 0. Standard error: empty. Validation: Exact stdout comparison. System-dependent values above are one recorded run.