for-ray.js

class Store{
  constructor(){
    this.store = new Map();
  }
  
  put(key, value, ttl){
    ttl = Date.now() + ttl;
    this.store.set(key, {value,ttl});
    this._cleanOldKeys();
  }
  
  get(key){
    const item = this.store.get(key);
    if (!item){
      return 'No key exists.';
    }
    
    if (Date.now() > item.ttl){
      this.store.delete(key);
      return 'Key has expired and has been removed.';
    }
    return item.value; 
  }
  
  _cleanOldKeys(){
    const timestamp = Date.now();
    for (let [key, data] of this.store){
      if (timestamp > data.ttl){
        this.store.delete(key);
      }
    }
  }
}

const myStore = new Store();

myStore.put('hello', 'goodbye', 4);
myStore.put('hello1', 'goodbye1', 4);
myStore.put('hello2', 'goodbye2', 4);
myStore.put('hello3', 'goodbye3', 4);
myStore.put('hello3', 'goodbye3', 4);

setTimeout(()=> { 
  myStore.put('hello3', 'goodbye3', 4);
  console.log('Attempt to get hello key: ',myStore.get('hello'));
  console.log('Attempt to get key that never existed: ',myStore.get('blank-key'));
  console.log('Date.now', Date.now());
  console.log('myStore: ',myStore.store);
}, 50);

To run:

node for-ray.js

Sample output:

Attempt to get hello key:  No key exists.
Attempt to get key that never existed:  No key exists.
Date.now 1597172027562
myStore:  Map { 'hello3' => { value: 'goodbye3', ttl: 1597172027565 } }

Switched over to Map data type from Object because:

• Maps can retrieve size from size property
• Maps have no default keys, no chance of key collision.