// LRU Cache----------
// 1. LRU is evicted; based on if the size of the Cache grows// Cache is implemented using JS Map - Instant Lookup O(1), Map reserves the insertion order; // 2. Persistent Storage - Implemented using a Set (Unique); Storage persist unless Cleared// clearData();// Since ES6 provides built-in *iterators*  for the collection types  // Array, Set, and Map, you don’t have to create iterators for these objects.// 3. TimeStamp is important - Time precision issue /** * @typedef {object} OriginData * @property {string} origin * @property {number} lastUsed * @property {number} size * @property {boolean} persistent */class MyLRUStorage  {  /**   * @param {number} capacity   * @param {() => number} getTimestamp   */  constructor(capacity, getTimestamp) {    this.capacity = capacity    this.getTimestamp = getTimestamp    // Cache using Map - get, set, has, delete    this.LRU = new Map();    this.persistentSet = new Set();    this.totalCacheSize = 0;  }  /**   * @param {string} origin   * @returns {OriginData | undefined}   */  getData(origin) {    // Get operation will mean we accesses the key so it becomes    // most recently used (MRU) - Move it to the front!    if (!this.LRU.has(origin)) {      return undefined;    }    const OriginData = this.LRU.get(origin);    // Adjust as MRU - delete and set it in front/recent    this.LRU.delete(origin);    this.LRU.set(origin, { size: OriginData.size });    return OriginData  }  /**   * @param {string} origin   * @param {number} size   * @returns {boolean}   */  setData(origin, size) {   // Will have to do the LRU Eviction   // Check if the size of origin is greater than size of cache   if (size > this.capacity) {     return false;   }   // If the new size is less than or equal to the originData.size   // JS Map.get returns an undefined if the valus is not present   if (this.LRU.has(origin) && this.LRU.get(origin).size >= size) {     // update the total size      this.totalCacheSize = this.totalCacheSize + size - this.LRU.get(origin).size     this.LRU.delete(origin);     this.LRU.set(origin, { size: size });     return true;   }    // Get the entries in the LRU    const LRUEntriesIterator = this.LRU.entries(); // List of OriginData List   // Keep evicting the LRU till we have enough size   while (this.totalCacheSize + size > this.capacity) {     const evictedSize = this.evict(LRUEntriesIterator);     if (evictedSize === undefined) {       return false;     }     this.totalCacheSize = this.totalCacheSize - evictedSize;   }   /// Now set the new origin   this.LRU.set(origin, { size });   // Update the totalCacheSize    this.totalCacheSize += size;    return true;  }  evict(LRUEntriesIterator) {   for (let [key, value] of LRUEntriesIterator) {     if (this.persistentSet.has(key)) {       continue;     }          this.LRU.delete(key);     // *** IMP - Returning from a for loop     // The return statement stops a loop only if it's inside the function     //  (i.e. it terminates both the loop and the function)     return value.size;   }    return;  }  /**   * @param {string} origin   * @returns {void}   */  clearData(origin) {   // Removes the data from Persistent Storage   this.persistentSet.delete(origin);   // delete from the map   const OriginData = this.LRU.get(origin);   if (OriginData && OriginData.size) {     this.totalCacheSize -= OriginData.size;   }   this.LRU.delete(origin);  }  /**   * @param {string} origin   * @returns {void}   */  makePersistent(origin) {    this.persistentSet.add(origin);  }}