Initial data commit

Task/Power-set/JavaScript/power-set-4.js

@@ -0,0 +1,19 @@
+(() => {
+    'use strict';
+
+    // powerset :: [a] -> [[a]]
+    const powerset = xs =>
+        xs.reduceRight((a, x) => [...a, ...a.map(y => [x, ...y])], [
+            []
+        ]);
+
+
+    // TEST
+    return {
+        '[1,2,3] ->': powerset([1, 2, 3]),
+        'empty set ->': powerset([]),
+        'set which contains only the empty set ->': powerset([
+            []
+        ])
+    };
+})()