problems(js): add “2622. Cache With Time Limit”

Signed-off-by: Matej Focko <me@mfocko.xyz>

problems/cache-with-time-limit.js

@@ -0,0 +1,46 @@
+var TimeLimitedCache = function() {
+    this.cache = new Map();
+};
+
+/**
+ * @param {number} key
+ * @param {number} value
+ * @param {number} time until expiration in ms
+ * @return {boolean} if un-expired key already existed
+ */
+TimeLimitedCache.prototype.set = function(key, value, duration) {
+    const existing = this.cache.get(key);
+    if (existing) {
+        clearTimeout(existing.ttl);
+    }
+
+    const ttl = setTimeout(() => this.cache.delete(key), duration);
+    this.cache.set(key, { value, ttl });
+    return Boolean(existing);
+};
+
+/**
+ * @param {number} key
+ * @return {number} value associated with key
+ */
+TimeLimitedCache.prototype.get = function(key) {
+    if (!this.cache.has(key)) {
+        return -1;
+    }
+    return this.cache.get(key).value;
+};
+
+/**
+ * @return {number} count of non-expired keys
+ */
+TimeLimitedCache.prototype.count = function() {
+    return this.cache.size;
+};
+
+/**
+ * Your TimeLimitedCache object will be instantiated and called as such:
+ * var obj = new TimeLimitedCache()
+ * obj.set(1, 42, 1000); // false
+ * obj.get(1) // 42
+ * obj.count() // 1
+ */