How do you implement a custom DNS resolver in Node.js?

Question

Accepted Answer

**DNS resolver** — resolve domain names with custom logic.

```javascript
const dns = require("dns").promises;

class CustomResolver {
    constructor() {
        this.cache = new Map();
        this.cacheTTL = 300000; // 5 min
    }

async resolve(hostname) {
        const cached = this.cache.get(hostname);
        if (cached && Date.now() - cached.timestamp < this.cacheTTL) {
            return cached.addresses;
        }

const addresses = await dns.resolve4(hostname);
        this.cache.set(hostname, {
            addresses,
            timestamp: Date.now(),
        });

return addresses;
    }

clearCache() {
        this.cache.clear();
    }
}

// Usage
const resolver = new CustomResolver();
const addresses = await resolver.resolve("example.com");
console.log(addresses);
```

**DNS over HTTPS:**
```javascript
async function resolveDoH(hostname) {
    const url = `https://dns.google/resolve?name=${hostname}&type=A`;
    const response = await fetch(url);
    const data = await response.json();
    return data.Answer?.map(a => a.data) || [];
}
```

Node.js: How do you implement a custom DNS resolver in Node.js?