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Grokking Node.js Design Patterns for Interviews

Solution: Measure Execution Time for an Async Task

Explore how to use the decorator pattern to measure execution time for asynchronous tasks in Node.js. Learn to wrap async functions to log durations transparently, preserving original functionality without modifying core logic.

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Solution explanation

  • Lines 2–6: We define fetchUser, a mock async service that resolves after 100 ms. It simulates an I/O call such as fetching from a database or API.

  • Lines 9–17: We build withTiming(fn), a decorator that:

    • Captures the start time with Date.now() before calling the original function. ...