> ## Documentation Index
> Fetch the complete documentation index at: https://developers.namuai-lab.com/llms.txt
> Use this file to discover all available pages before exploring further.
# Build a Hausa ⇄ French interpreter
> A web page where one person speaks Hausa, the other hears French, and back again.
12 min
Build a Hausa ⇄ French interpreter
**You will build:** a one-page web app with two buttons, *Hausa → French* and *French → Hausa*. Hold a button, speak, release: the page shows what was understood, the translation, and plays it aloud. One API call per turn.
**You will need:** Node 23.6+ to run the `.ts` file directly (or compile it), `npm install express multer namu-ai` ([JavaScript library](https://developers.namuai-lab.com/sdks/javascript.md)), and `NAMU_API_KEY` set.
**1. The server**
It receives the browser's recording, calls `/v1/translate` with `include_audio`, and returns the result. The key never leaves it.
```typescript server.ts theme={null}
import express from "express";
import multer from "multer";
import { Namu, NamuError } from "namu-ai";
const app = express();
const upload = multer({ limits: { fileSize: 25 * 1024 * 1024 } });
const namu = new Namu();
app.use(express.static("public"));
app.post("/translate", upload.single("file"), async (req, res) => {
const source = req.body.source === "fr" ? "fr" : "ha";
const target = source === "ha" ? "fr" : "ha";
try {
const result = await namu.translate({ audio: req.file!.buffer }, { source, target, includeAudio: true });
res.json({ heard: result.source_text, text: result.text, audio: result.audio });
} catch (err) {
const type = err instanceof NamuError ? err.type : "unavailable";
res.status(err instanceof NamuError ? err.status : 502).json({ error: type });
}
});
app.listen(3000, () => console.log("http://localhost:3000"));
```
**2. The page**
The browser records with `MediaRecorder` (WebM Opus), which the API reads as it is.
```html public/index.html theme={null}
Interpreter
```
**3. Run it**
```bash theme={null}
node server.ts
```
Open `http://localhost:3000`, allow the microphone, hold a button and speak.
## Before real people use it
* Put your own sign-in in front of `/translate`, or anyone who finds the page spends your allowance.
* Show `heard` so both people can see what was understood; that is often where a misunderstanding starts.
* For health, legal or money conversations, keep a human interpreter in the loop.
## Next
> [card] [Translation](https://developers.namuai-lab.com/capabilities/translation.md)
>
> Every option
> [card] [Building for weak networks](https://developers.namuai-lab.com/guides/weak-networks.md)
>
> Make it work on 3G
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