How do you implement a custom file watcher in Node.js?

Question

Accepted Answer

**File watcher** — monitor file changes.

```javascript
const fs = require("fs");

class FileWatcher {
    constructor() {
        this.watchers = new Map();
    }

watch(path, callback, options = {}) {
        const watcher = fs.watch(path, options, (eventType, filename) => {
            callback({
                type: eventType,
                file: filename,
                timestamp: Date.now(),
            });
        });

this.watchers.set(path, watcher);
        return () => this.unwatch(path);
    }

unwatch(path) {
        const watcher = this.watchers.get(path);
        if (watcher) {
            watcher.close();
            this.watchers.delete(path);
        }
    }

unwatchAll() {
        this.watchers.forEach(w => w.close());
        this.watchers.clear();
    }
}

// Usage
const watcher = new FileWatcher();

watcher.watch("./config", ({ type, file }) => {
    console.log(`File ${type}: ${file}`);
    if (file === "config.json") reloadConfig();
});
```

**chokidar (more reliable):**
```javascript
const chokidar = require("chokidar");
const watcher = chokidar.watch("./src", { ignoreInitial: true });
watcher.on("change", (path) => console.log("Changed:", path));
```

Node.js: How do you implement a custom file watcher in Node.js?