test-c.js

function Cache(size) {
  this.store = {};
  this.size = size;
  this.get = function(k){
    this.store[k].d = Date.now();
    return this.store[k].v;
  };
  this.put = function(k, v) {
    let objKeys = Object.keys(this.store);
    if(objKeys.length < this.size){
      this.store[k] = { v, d: Date.now() };
    } else {
      let lrd = Date.now();
      let lro;
      for(let i in objKeys){
        if(this.store[i] < lrd){
          lro = i;
        }
      }
      delete this.store[lro];
      this.store[k] = { v, d: Date.now() };
    }
  };
  this.all = function() {
    return this.store;
  }
}

cache = new Cache(2) // capacity = 2
cache.put(1, "1")
cache.put(2, "2")
console.log(cache.get(1)) // returns "1"
cache.put(3, "3") // evicts key 2, because the key 1 was retrieved
console.log(cache.get(2)) // returns null, because 2 was just evicted
cache.put(4, "4") // evicts key 1,
console.log(cache.get(1)) // returns null, because it was evicted earlier
console.log(cache.get(3)) // returns "3"
console.log(cache.get(4)) // returns "4"
console.log(cache.all());