Which Approach to Choose?

Two ways to create objects with methods — each with different trade-offs:

Prototype Methods (Memory-Efficient)

Methods defined ONCE on the prototype, shared by all instances:

function Counter(start) { this.count = start; }
Counter.prototype.increment = function() { this.count++; };

// 1,000 Counters share ONE method in memory ✅

✅ Massive memory savings ⚠️ Methods are public — no true private state

Closure Methods (Private State)

Methods created anew for each object:

function createCounter(start) {
  let count = start; // Truly private!
  return {
    increment() { count++; },
    getCount() { return count; }
  };
}
// 1,000 counters = 1,000 copies of each method in memory ⚠️

✅ True private variables — strong encapsulation ⚠️ Higher memory usage with many instances