LRU Cache with hash table and double linked list

Author: EasyHard

lru-cache.js

@@ -0,0 +1,88 @@
+var DEBUG = process.env.DEBUG;
+
+function Node(k, v, prev, next) {
+  this.k = k;
+  this.v = v;
+  this.prev = prev;
+  this.next = next;
+}
+
+Node.prototype.remove = function () {
+  var prev = this.prev;
+  var next = this.next;
+  prev.next = next;
+  next.prev = prev;
+};
+Node.prototype.insertAfter = function (node) {
+  var next = this.next;
+  this.next = node;
+  node.next = next;
+  node.prev = this;
+  next.prev = node;
+};
+/**
+ * @constructor
+ */
+var LRUCache = function(capacity) {
+  this.head = new Node();
+  this.tail = new Node();
+  this.head.next = this.tail;
+  this.tail.prev = this.head;
+  this.m = {};
+  this.size = 0;
+  this.capacity = capacity;
+};
+
+/**
+ * @param {number} key
+ * @returns {number}
+ */
+LRUCache.prototype.get = function(key) {
+  if (this.m[key]) {
+    this.lift(this.m[key]);
+    return this.m[key].v;
+  } else {
+    return -1;
+  }
+};
+
+LRUCache.prototype.lift = function (node) {
+  node.remove();
+  this.head.insertAfter(node);
+};
+
+/**
+ * @param {number} key
+ * @param {number} value
+ * @returns {void}
+ */
+LRUCache.prototype.set = function(key, value) {
+  var node;
+  if (this.m[key]) {
+    node = this.m[key];
+    this.lift(node);
+    node.v = value;
+  } else {
+    if (this.size === this.capacity) {
+      var r = this.tail.prev;
+      delete this.m[r.k];
+      r.remove();
+      this.size--;
+    }
+    node = new Node(key, value);
+    this.head.insertAfter(node);
+    this.m[key] = node;
+    this.size++;
+  }
+};
+
+if (DEBUG) {
+  var cache = new LRUCache(1);
+  cache.set(2, 1);
+  console.log(cache.get(2));
+  cache.set(2, 3);
+  console.log(cache.get(2));
+  cache.set(4, 3);
+  console.log(cache.get(2));
+  console.log(cache.get(4));
+}