Grokking Node.js Design Patterns for Interviews/

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Solution: Add Caching Without Touching Core Logic

Solution: Add Caching Without Touching Core Logic

Use a stateful decorator to add caching (memoization) around an async function, improving performance without changing its logic.

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Solution explanation

  • Lines 2–7: We define getProductDetails, a simulated async API call. It logs every fetch and resolves after 150 ms, representing a costly service operation.

  • Lines 10–26: We create withCache(fn), a stateful decorator:

    • We initialize a Map named cache to store results.

    • Inside the returned async wrapper, we compute a cache key by serializing the arguments with JSON.stringify.

    • If the ...