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DesignPatternsintermediate

Observer — Emit with no listeners

📖 Usage Example
const emitter = createEmitter();
emitter.emit('test'); // no listeners — no error

Emitting with no listeners should be a no-op — not throw an error.

Observer Pattern — Safe Emit

The emit method should handle events that have no subscribers without throwing an error.

Challenge: Implement an EventEmitter that safely emits events even when no listeners are subscribed.

Example:

const emitter = new EventEmitter()
emitter.emit('nonexistent') // Should not throw
expect((() => { try { emitter.emit('test'); return true; } catch(e) { return false; } })()).toBe(true)
💡 Hints (3)
  • • Use nullish coalescing to default to empty array
  • • forEach on empty array does nothing
  • • No error handling needed if you use the nullish operator