مشاهدة ملف: LRUCache.js

"use strict";

Object.defineProperty(exports, "__esModule", {
  value: true
});
exports["default"] = void 0;

function _defineProperties(target, props) { for (var i = 0; i < props.length; i++) { var descriptor = props[i]; descriptor.enumerable = descriptor.enumerable || false; descriptor.configurable = true; if ("value" in descriptor) descriptor.writable = true; Object.defineProperty(target, descriptor.key, descriptor); } }

function _createClass(Constructor, protoProps, staticProps) { if (protoProps) _defineProperties(Constructor.prototype, protoProps); if (staticProps) _defineProperties(Constructor, staticProps); Object.defineProperty(Constructor, "prototype", { writable: false }); return Constructor; }

function _classCallCheck(instance, Constructor) { if (!(instance instanceof Constructor)) { throw new TypeError("Cannot call a class as a function"); } }

// https://medium.com/dsinjs/implementing-lru-cache-in-javascript-94ba6755cda9
var Node = /*#__PURE__*/_createClass(function Node(key, value) {
  var next = arguments.length > 2 && arguments[2] !== undefined ? arguments[2] : null;
  var prev = arguments.length > 3 && arguments[3] !== undefined ? arguments[3] : null;

  _classCallCheck(this, Node);

  this.key = key;
  this.value = value;
  this.next = next;
  this.prev = prev;
});

var LRUCache = /*#__PURE__*/function () {
  //set default limit of 10 if limit is not passed.
  function LRUCache() {
    var limit = arguments.length > 0 && arguments[0] !== undefined ? arguments[0] : 10;

    _classCallCheck(this, LRUCache);

    this.size = 0;
    this.limit = limit;
    this.head = null;
    this.tail = null;
    this.cache = {};
  } // Write Node to head of LinkedList
  // update cache with Node key and Node reference


  _createClass(LRUCache, [{
    key: "put",
    value: function put(key, value) {
      this.ensureLimit();

      if (!this.head) {
        this.head = this.tail = new Node(key, value);
      } else {
        var node = new Node(key, value, this.head);
        this.head.prev = node;
        this.head = node;
      } //Update the cache map


      this.cache[key] = this.head;
      this.size++;
    } // Read from cache map and make that node as new Head of LinkedList

  }, {
    key: "get",
    value: function get(key) {
      if (this.cache[key]) {
        var value = this.cache[key].value; // node removed from it's position and cache

        this.remove(key); // write node again to the head of LinkedList to make it most recently used

        this.put(key, value);
        return value;
      }

      console.log("Item not available in cache for key ".concat(key));
    }
  }, {
    key: "ensureLimit",
    value: function ensureLimit() {
      if (this.size === this.limit) {
        this.remove(this.tail.key);
      }
    }
  }, {
    key: "remove",
    value: function remove(key) {
      var node = this.cache[key];

      if (node.prev !== null) {
        node.prev.next = node.next;
      } else {
        this.head = node.next;
      }

      if (node.next !== null) {
        node.next.prev = node.prev;
      } else {
        this.tail = node.prev;
      }

      delete this.cache[key];
      this.size--;
    }
  }, {
    key: "clear",
    value: function clear() {
      this.head = null;
      this.tail = null;
      this.size = 0;
      this.cache = {};
    } // // Invokes the callback function with every node of the chain and the index of the node.
    // forEach(fn) {
    //   let node = this.head;
    //   let counter = 0;
    //   while (node) {
    //     fn(node, counter);
    //     node = node.next;
    //     counter++;
    //   }
    // }
    // // To iterate over LRU with a 'for...of' loop
    // *[Symbol.iterator]() {
    //   let node = this.head;
    //   while (node) {
    //     yield node;
    //     node = node.next;
    //   }
    // }

  }]);

  return LRUCache;
}();

exports["default"] = LRUCache;
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