diff --git a/array-dot-diff-hero/index.js b/array-dot-diff-hero/index.js
new file mode 100644
index 0000000..2327c85
--- /dev/null
+++ b/array-dot-diff-hero/index.js
@@ -0,0 +1,15 @@
+// https://www.codewars.com/kata/array-dot-diff-hero
+
+function array_diff_very_fast(a, b) {
+  const diff = [];
+  const set = new Set();
+  for (let i = 0; i < b.length; ++i) {
+    set.add(b[i]);
+  }
+  for (let i = 0; i < a.length; ++i) {
+    if (!set.has(a[i])) {
+      diff.push(a[i]);
+    }
+  }
+  return diff;
+}