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Grokking Node.js Design Patterns for Interviews

Solution: Calculate Prices for Experiment Groups

Explore how to apply the Strategy Pattern to implement dynamic pricing algorithms for different experiment groups in Node.js. Understand how to encapsulate pricing strategies like conservative, aggressive, and dynamic markups, and swap these strategies at runtime without altering core business logic.

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Solution explanation

  • Lines 2–22: We define three distinct pricing strategies: ConservativePricing, AggressivePricing, and DynamicPricing.

    • Each exposes .calculate(basePrice) and returns a formatted numeric price.

    • ConservativePricing applies a 5% markup for stability.

    • AggressivePricing applies a 25% markup to maximize margin.

    • DynamicPricing introduces random variation, simulating algorithmic pricing experiments.

  • Lines 25–38: The PricingService class acts as the context.

    • It receives one strategy and delegates computation to it through .calculate().

    • .setStrategy() allows runtime replacement of pricing behavior.

    • This keeps the business workflow stable while isolating ...