Add an internal function to refresh timer used for ttl

src/index.ts

@@ -4,7 +4,7 @@
 
 // module-private names and types
 type Perf = { now: () => number }
-const perf: Perf =
+let perf: Perf =
   typeof performance === 'object' &&
   performance &&
   typeof performance.now === 'function'
@@ -1259,6 +1259,7 @@ export class LRUCache<K extends {}, V extends {}, FC = unknown> {
         c.#rindexes(options),
       isStale: (index: number | undefined) =>
         c.#isStale(index as Index),
+      refreshTTLTimerReference: () => c.#refreshTTLTimerReference(),
     }
   }
 
@@ -1557,6 +1558,15 @@ export class LRUCache<K extends {}, V extends {}, FC = unknown> {
     }
   }
 
+  #refreshTTLTimerReference() {
+    perf =
+      typeof performance === 'object' &&
+      performance &&
+      typeof performance.now === 'function'
+        ? performance
+        : Date
+  }
+
   // conditionally set private methods related to TTL
   #updateItemAge: (index: Index) => void = () => {}
   #statusTTL: (status: LRUCache.Status<V>, index: Index) => void =

test/ttl-timer-refresh.ts

@@ -0,0 +1,35 @@
+if (typeof performance === 'undefined') {
+  global.performance = require('perf_hooks').performance
+}
+import t from 'tap'
+import { LRUCache } from '../dist/esm/index.js'
+import { expose } from './fixtures/expose.js'
+
+t.test('ttl timer refresh', async t => {
+  // @ts-ignore
+  global.performance = {
+    now: () => 5,
+  }
+  const { LRUCache: LRU } = t.mockRequire('../', {})
+  const c = new LRU({ max: 5, ttl: 10, ttlResolution: 0 })
+  const e = expose(c, LRU)
+
+  c.set('a', 1)
+
+  const status: LRUCache.Status<any> = {}
+  c.get('a', { status })
+  t.equal(status.now, 5)
+
+  // New timer mock
+  // @ts-ignore
+  global.performance = {
+    now: () => 10,
+  }
+
+  c.get('a', { status })
+  t.equal(status.now, 5, 'still using the old ttl timer')
+
+  e.refreshTTLTimerReference()
+  c.get('a', { status })
+  t.equal(status.now, 10, 'using the new ttl timer')
+})