1 files changed, 33 insertions, 0 deletions
diff --git a/src/app/use_timer.ts b/src/app/use_timer.ts
new file mode 100644
index 0000000..487591d
--- /dev/null
+++ b/src/app/use_timer.ts
@@ -0,0 +1,33 @@
+import { useEffect, useState, useCallback } from "react";
+
+function useTimer(speed = 1) {
+  const [paused, setPaused] = useState(true);
+  const play = useCallback(() => setPaused(false), []);
+  const pause = useCallback(() => setPaused(true), []);
+
+  const [currentMillisecond, setCurrentMillisecond] = useState(0);
+  const reset = useCallback(() => setCurrentMillisecond(0), []);
+
+  useEffect(() => {
+    if (!paused) {
+      let last = Date.now();
+      const timer = window.setInterval(() => {
+        const now = Date.now();
+        setCurrentMillisecond((cm) => cm + (now - last) * speed);
+        last = now;
+      }, 97);
+      return () => window.clearInterval(timer);
+    }
+  }, [paused, speed]);
+
+  return {
+    currentMillisecond,
+    setCurrentMillisecond,
+    reset,
+    paused,
+    play,
+    pause
+  };
+}
+
+export default useTimer;
+\ No newline at end of file