中文
devexamples

Generic Cache With Eviction Hook

Build a key-value cache that is generic over value type and fires an eviction callback, so callers get typed reads and can clean up resources.

TypescriptData Fetching

Code

snippet
export class TypedCache<K, V> {
  private store = new Map<K, { value: V; expiresAt: number }>();

  constructor(
    private ttlMs: number,
    private onEvict?: (key: K, value: V) => void,
  ) {}

  get(key: K): V | undefined {
    const entry = this.store.get(key);
    if (!entry) return undefined;
    if (entry.expiresAt <= Date.now()) {
      this.store.delete(key);
      this.onEvict?.(key, entry.value);
      return undefined;
    }
    return entry.value;
  }

  set(key: K, value: V): void {
    if (this.store.has(key)) {
      const previous = this.store.get(key)!;
      this.onEvict?.(key, previous.value);
    }
    this.store.set(key, { value, expiresAt: Date.now() + this.ttlMs });
  }

  size(): number {
    return this.store.size;
  }
}

Related Examples