Help the bookseller

help-the-bookseller/index.js

@@ -0,0 +1,10 @@
+// https://www.codewars.com/kata/54dc6f5a224c26032800005c/solutions/javascript
+
+function stockList(art, cat) {
+  const arr = cat.map(c => {
+    return [c, art.filter(a => a[0] === c).reduce((a, b) => {
+      return a + +b.match(/\d+/);
+    }, 0)];
+  });
+  return arr.reduce((a, [c, v]) => a + v, 0) && arr.map(([c, v]) => `(${c} : ${v})`).join` - ` || '';
+}