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* @description lru缓存算法。指定缓存空间长度，当缓存超出时，清除最不活跃的缓存。
* @author liukun <919590347@qq.com>
* @example
* import { LRUCache } from '@wont/utils'
*
* const lru = new LRUCache(3);
* lru.set(1, 1);
* lru.set(2, 2);
* lru.set(3, 3);
* lru.set(4, 4);
* lru.set(4, 5);
* console.info(lru.get()); // return Map(3) { 2 => 2, 3 => 3, 4 => 5 }
*/
export class LRUCache {
#map: Map<unknown, unknown>
#length: number
/**
* 创建LRUCache实例
* @param {number} [len=0] - lru缓存上限，默认为0，无上限。
*/
constructor(len = 0) {
this.#map = new Map()
this.#length = len
}
/**
* 检测是否有缓存
* @param {unknown} key - The key to check.
* @returns {boolean} 是否存在缓存
*/
has(key: unknown): boolean {
return this.#map.has(key)
}
/**
* 通过key获取缓存。如果存在缓存，则更新为最近使用。
* @param {unknown} key - The key to retrieve the value for.
* @returns {unknown | null | Map<unknown, unknown>} 不存在返回null。key不传返回全部缓存map
*/
get(key?: unknown): unknown | null | Map<unknown, unknown> {
if (!key) {
return this.#map
}
if (!this.has(key)) {
return null
}
const val = this.#map.get(key)
this.#map.delete(key)
this.#map.set(key, val)
return this.#map.get(key)
}
/**
* 设置新增或修改缓存。并且将设置的缓存设置为最近使用
* @param {unknown} key - The key to set.
* @param {unknown} val - The value to set.
* @returns {undefined}
*/
set(key: unknown, val: unknown): void {
if (this.has(key)) {
this.#map.delete(key)
}
this.#map.set(key, val)
if (this.#length > 0 && this.#map.size > this.#length) {
const firstEle = this.#map.keys().next().value
this.#map.delete(firstEle)
}
}
}
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