JS 实现 一个 LRU (最近最少使用) 缓存机制。

class LRU {
        //capacity :  缓存的容量
        constructor(capacity) {
            this.capacity = capacity;
            this.map = new Map()
        }
        get(key) {
            let val = this.map.get(key);
            if (val === "undefined") return -1;
            this.map.delete(key);
            this.map.set(key, val)
        }
        put(key, val) {
            if (this.map.has(key)) {
                this.map.delete(key);
            }
            this.map.set(key, val)
            let keys = this.map.keys()
            while (this.capacity < this.map.size) {
                this.map.delete(keys.next().value)
            }
        }
    }
    let lru = new LRU(3)
    lru.put(1, "y")
    lru.put(2, "z")
    lru.put(3, "x")
    lru.put(4, "yx")
    lru.get(2)
    lru.put(8, "u")
    console.log(lru);