From 34adaed7992e6f7e5ea7aa7fcda86c6c2caa5f04 Mon Sep 17 00:00:00 2001
From: koronya <koronya@hanmail.net>
Date: Thu, 14 May 2026 20:44:46 +0900
Subject: [PATCH] [JS][7kyu] Music 1: How Many Quarter Notes?

---
 .../music-1-how-many-quarter-notes/koronya.js | 30 +++++++++++++++++++
 1 file changed, 30 insertions(+)
 create mode 100644 codewars/7kyu/music-1-how-many-quarter-notes/koronya.js

diff --git a/codewars/7kyu/music-1-how-many-quarter-notes/koronya.js b/codewars/7kyu/music-1-how-many-quarter-notes/koronya.js
new file mode 100644
index 000000000..0a01d07a1
--- /dev/null
+++ b/codewars/7kyu/music-1-how-many-quarter-notes/koronya.js
@@ -0,0 +1,30 @@
+// [JS][7kyu] Music 1: How Many Quarter Notes?
+// music-1-how-many-quarter-notes
+// https://www.codewars.com/kata/69c2f04a1294ffc95c526d9e/train/javascript
+
+const findQuarterNotes = (timeSignature) => {
+  const [a, b] = timeSignature.split('/').map(Number)
+  if ((Math.log(b) / Math.log(2)) % 1 !== 0) {
+    return null
+  }
+  return Math.floor((a / b) * 4)
+}
+
+findQuarterNotes('4/4') === 4
+findQuarterNotes('3/4') === 3
+
+findQuarterNotes('6/8') === 3
+findQuarterNotes('9/8') === 4
+
+findQuarterNotes('1/8') === 0
+findQuarterNotes('1/16') === 0
+
+findQuarterNotes('9/0') === null
+findQuarterNotes('7/3') === null
+findQuarterNotes('6/5') === null
+findQuarterNotes('5/6') === null
+findQuarterNotes('3/7') === null
+findQuarterNotes('0/9') === null
+
+findQuarterNotes('7/1') === 28
+findQuarterNotes('6/2') === 12