Website Structure

Frontend-Learner/node_modules/ylru/index.js

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+'use strict';
+
+class LRU {
+  constructor(max) {
+    this.max = max;
+    this.size = 0;
+    this.cache = new Map();
+    this._cache = new Map();
+  }
+
+  get(key, options) {
+    let item = this.cache.get(key);
+    const maxAge = options && options.maxAge;
+    // only call Date.now() when necessary
+    let now;
+    function getNow() {
+      now = now || Date.now();
+      return now;
+    }
+    if (item) {
+      // check expired
+      if (item.expired && getNow() > item.expired) {
+        item.expired = 0;
+        item.value = undefined;
+      } else {
+        // update expired in get
+        if (maxAge !== undefined) {
+          const expired = maxAge ? getNow() + maxAge : 0;
+          item.expired = expired;
+        }
+      }
+      return item.value;
+    }
+
+    // try to read from _cache
+    item = this._cache.get(key);
+    if (item) {
+      // check expired
+      if (item.expired && getNow() > item.expired) {
+        item.expired = 0;
+        item.value = undefined;
+      } else {
+        // not expired, save to cache
+        this._update(key, item);
+        // update expired in get
+        if (maxAge !== undefined) {
+          const expired = maxAge ? getNow() + maxAge : 0;
+          item.expired = expired;
+        }
+      }
+      return item.value;
+    }
+  }
+
+  set(key, value, options) {
+    const maxAge = options && options.maxAge;
+    const expired = maxAge ? Date.now() + maxAge : 0;
+    let item = this.cache.get(key);
+    if (item) {
+      item.expired = expired;
+      item.value = value;
+    } else {
+      item = {
+        value,
+        expired,
+      };
+      this._update(key, item);
+    }
+  }
+
+  keys() {
+    const cacheKeys = new Set();
+    const now = Date.now();
+
+    for (const entry of this.cache.entries()) {
+      checkEntry(entry);
+    }
+
+    for (const entry of this._cache.entries()) {
+      checkEntry(entry);
+    }
+
+    function checkEntry(entry) {
+      const key = entry[0];
+      const item = entry[1];
+      if (entry[1].value && (!entry[1].expired) || item.expired >= now) {
+        cacheKeys.add(key);
+      }
+    }
+
+    return Array.from(cacheKeys.keys());
+  }
+
+  reset() {
+    this.size = 0;
+    this.cache.clear();
+    this._cache.clear();
+  }
+
+  _update(key, item) {
+    this.cache.set(key, item);
+    this.size++;
+    if (this.size >= this.max) {
+      this.size = 0;
+      this._cache = this.cache;
+      this.cache = new Map();
+    }
+  }
+}
+
+module.exports = LRU;
+