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+# 28. implement clearAllTimeout()
+
+### Problem
+
+https://bigfrontend.dev/problem/implement-clearAllTimeout
+
+#
+
+### Problem Description
+
+`window.setTimeout()` could be used to schedule some task in the future.
+
+Could you implement `clearAllTimeout()` to clear all the timers? This might be useful when we want to clear things up before page transition.
+
+For example
+
+```js
+setTimeout(func1, 10000);
+setTimeout(func2, 10000);
+setTimeout(func3, 10000);
+// all 3 functions are scheduled 10 seconds later
+
+clearAllTimeout();
+// all scheduled tasks are cancelled.
+```
+
+**note**
+
+You need to keep the interface of `window.setTimeout` and `window.clearTimeout` the same, but you could replace them with new logic
+
+#
+
+### Solution
+
+```js
+const timerCache = new Set();
+const originalSetTimeout = window.setTimeout;
+
+window.setTimeout = (cb, delay) => {
+  const timer = originalSetTimeout(cb, delay);
+  timerCache.add(timer);
+  return timer;
+};
+
+/**
+ * cancel all timer from window.setTimeout
+ */
+function clearAllTimeout() {
+  for (const timer of timerCache) {
+    clearTimeout(timer);
+  }
+}
+```