Grokking Node.js Design Patterns for Interviews/

...

/

Solution: Bridge Callback and Promise APIs

Solution: Bridge Callback and Promise APIs

Convert a callback-based database client into a modern promise-based interface using an adapter.

We'll cover the following...

Solution explanation

  • Lines 2–12: We simulate a legacy database client using callbacks.

    • It exposes a query(sql, callback) method.

    • If the SQL string contains "error", it triggers a failure.

    • Otherwise, it calls the callback with fake data after a short delay.

    • This models a real callback-style API you’d see in older Node.js libraries.

  • Lines 15–17: The DbClientAdapter constructor accepts the legacy client.

...