LRUCache Class — react Architecture

Source Code

packages/eslint-plugin-react-hooks/src/shared/RunReactCompiler.ts lines 265–299

class LRUCache<K, T> {
  // newest at headIdx, then headIdx + 1, ..., tailIdx
  #values: Array<[K, T | Error] | [typeof SENTINEL, void]>;
  #headIdx: number = 0;

  constructor(size: number) {
    this.#values = new Array(size).fill(SENTINEL);
  }

  // gets a value and sets it as "recently used"
  get(key: K): T | null {
    const idx = this.#values.findIndex(entry => entry[0] === key);
    // If found, move to front
    if (idx === this.#headIdx) {
      return this.#values[this.#headIdx][1] as T;
    } else if (idx < 0) {
      return null;
    }

    const entry: [K, T] = this.#values[idx] as [K, T];

    const len = this.#values.length;
    for (let i = 0; i < Math.min(idx, len - 1); i++) {
      this.#values[(this.#headIdx + i + 1) % len] =
        this.#values[(this.#headIdx + i) % len];
    }
    this.#values[this.#headIdx] = entry;
    return entry[1];
  }
  push(key: K, value: T): void {
    this.#headIdx =
      (this.#headIdx - 1 + this.#values.length) % this.#values.length;
    this.#values[this.#headIdx] = [key, value];
  }
}