LRU Cache Implementation

lru_cache.js

class LruCache {
    constructor(capacity) {
        this.capacity = capacity;
        this.map = new Map();
    }

    get(key) {
        if(this.map.has(key)) {
            let val = this.map.get(key);
            this.map.delete(key);
            this.map.set(key, val)
            return val;
        }
        return -1
    }

    put(key, val) {
        if(this.get(key) === -1) {
            if(this.capacity === this.map.size && this.map.size > 0) {
                const keys = this.map.keys();
                this.map.delete(keys.next().value);
            }
        }
        this.map.set(key, val);
    }
}

const lc = new LruCache(2);
lc.put(1, 1) // [1 => 1]
lc.put(2, 2) // [1 => 1, 2 => 2]
console.assert(lc.get(1), 1); // [2 => 2, 1 => 1]
lc.put(3, 3) // [1 => 1, 3 => 3]
console.assert(lc.get(2), -1) // [1 => 1, 3 => 3]
lc.put(4, 4) // [3 => 3, 4 => 4]
console.assert(lc.get(1), -1) // [3 => 3, 4 => 4]
console.assert(lc.get(3), 3) // [4 => 4, 3 => 3]
console.assert(lc.get(4), 4) // [3 => 3, 4 => 4]