JavaScript client

Two packages on npm: @kotoshu/client, the typed HTTP client, and @kotoshu/wasm, the whole engine compiled to WebAssembly. Same Suggestion shape either way.

Install

npm install @kotoshu/client         # the HTTP client (ESM + TypeScript types)
npm install @kotoshu/wasm           # optional: the engine, 162 KiB gzipped (0.3.2 tarball)

Node 18+, Deno, Bun, and browsers. The wasm package is deliberately not a dependency of the client — opt in explicitly.

Quick start — over HTTP

Point the client at a running kotoshu-server:

import { Client } from "@kotoshu/client";

const client = new Client("http://127.0.0.1:9292");

const result = await client.check("helo wrold", "en");
for (const err of result.errors) {
console.log(err.word, "->", err.suggestions.slice(0, 3).map((s) => s.word));
}

const suggestions = await client.suggest("recieve", { max: 3 });
console.log(suggestions.map((s) => [s.word, s.confidence]));

console.log(await client.correct("hello", "en"));

helo -> [ 'hello', 'help', 'hell' ]
wrold -> [ 'world', 'wold', 'weld' ]
[ [ 'receive', 1 ], [ 'relieve', 0.91 ], [ 'recife', 0.5 ] ]
true

Offline — the wasm engine

With @kotoshu/wasm installed, createWasmDictionary loads the engine in-process. Dictionaries are the string contents of the .aff and .dic files — WebAssembly has no filesystem:

import { createWasmDictionary } from "@kotoshu/client/dist/wasm.js";

const aff = await (await fetch("/dictionaries/en.aff")).text();
const dic = await (await fetch("/dictionaries/en.dic")).text();

const dict = await createWasmDictionary(aff, dic);
if (dict) {
dict.correct("hello");      // true
dict.correct("helo");       // false
dict.suggest("hlelo", 3);   // ["hello", "halo", "heel"]
} else {
// backend resolved to "http" — use the Client instead
}

Choosing a backend

The option { backend } wins over the environment variable. Like the Python package, the offline engine is word-level — no document checking, no language detection. Errors are typed, with KotoshuError as the base and ResourceNotSetupError for the 422 case.

Verified 2026-09-05 — both quick starts executed against @kotoshu/client 0.1.0 and @kotoshu/wasm 0.1.0 on Node 24. Registry: @kotoshu/client on npm · @kotoshu/wasm on npm · kotoshu-js repo