# 使用 js 实现一个 lru cache
Issue
欢迎在 Gtihub Issue 中回答此问题: Issue 251 (opens new window)
Author
可以借助Map实现
class LRUCache {
constructor(limit) {
this.limit = limit;
this.cache = new Map();
}
get(key) {
if (!this.cache.has(key)) return undefined;
const value = this.cache.get(key);
this.cache.delete(key);
this.cache.set(key, value);
return value;
}
put(key, value) {
if (this.cache.has(key)) this.cache.delete(key);
else if (this.cache.size >= this.limit) {
this.cache.delete(this.cache.keys().next().value);
}
this.cache.set(key, value);
}
}
// ["LRUCache","put","put","get","put","get","put","get","get","get"]
// [[2],[1,1],[2,2],[1],[3,3],[2],[4,4],[1],[3],[4]]
const lruCache = new LRUCache(2);
lruCache.put(1, 1);
lruCache.put(2, 2);
const res1 = lruCache.get(1);
lruCache.put(3, 3);
const res2 = lruCache.get(2);
lruCache.put(4, 4);
const res3 = lruCache.get(1);
const res4 = lruCache.get(3);
const res5 = lruCache.get(4);
console.log(res1, res2, res3, res4, res5);
// 1 undefined undefined 3 4
Author
LRU (最近最少使用) 缓存机制
- 使用 Map 做数据保存
- 自建双向链表做元素使用频率保存及空间大小控制
Author
数组存 key + map
class LRUCache {
_stack = [];
_map = {};
constructor(len = 10) {
this._len = len;
}
put(key, value) {
if (this._stack.includes(key)) {
this.update(key, value);
return;
}
// 如果超过缓存的大小，那就删除数组中的最后一个值
if (this._stack.length >= this._len) {
const delKey = this._stack[this._len - 1];
this.delete(delKey);
}
this.set(key, value);
}
set(key, value) {
this._stack.unshift(key);
this._map[key] = value;
}
get(key) {
if (this._map[key]) {
this.update(key);
return this._map[key];
}
return -1;
}
update(key, value) {
const index = this._stack.indexOf(key);
this._stack.splice(index, 1);
this._stack.unshift(key);
if (value) {
this._map[key] = value;
}
}
delete(key) {
delete this._map[key];
this._stack.pop();
}
}
export default LRUCache;