Does Defining Methods via Constructor in JavaScript Create Duplicate Function Copies?

Performance Implications of Defining Methods via Prototype vs Constructor in JavaScript

In JavaScript, two approaches exist for creating "classes" with public functions: using the prototype or the constructor. Method 1 assigns functions to instances through the constructor, while Method 2 utilizes the prototype to share functions among all instances.

While Method 2 is often claimed to be more efficient, depriving instances of private instance variables is a significant disadvantage. However, does Method 1's apparent creation of duplicate function copies for each instance truly occur in practice?

Empirical Evidence from JsPerf Benchmark

JsPerf benchmarking suggests that Method 2 (prototype) indeed outperforms Method 1 (constructor) in terms of speed.

Practical Implications

While this difference is evident in benchmarks, its relevance in real-world applications is questionable. Even in scenarios with a significant number of object instantiations (e.g., 10,000 per frame), this micro-optimization is unlikely to alleviate performance bottlenecks.

Recommendations

If optimizing performance is crucial, declaring methods via the prototype is advisable. Otherwise, Method 1 provides greater flexibility and adheres to common object-oriented programming conventions. Additionally, the use of private properties denoted by an underscore prefix (e.g., _process()) enhances encapsulation and discourages direct modification.

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