Initial data commit

Task/Find-the-missing-permutation/JavaScript/find-the-missing-permutation-6.js

@@ -0,0 +1,39 @@
+(() => {
+    'use strict';
+
+    // main :: IO ()
+    const main = () => {
+        const xs = [
+            'ABCD', 'CABD', 'ACDB', 'DACB', 'BCDA', 'ACBD',
+            'ADCB', 'CDAB', 'DABC', 'BCAD', 'CADB', 'CDBA',
+            'CBAD', 'ABDC', 'ADBC', 'BDCA', 'DCBA', 'BACD',
+            'BADC', 'BDAC', 'CBDA', 'DBCA', 'DCAB'
+        ];
+
+        return xs.reduce(
+            (a, x) => zipWith(xor)(a)(codes(x)),
+            [0, 0, 0, 0]
+        ).map(x => String.fromCodePoint(x)).join('')
+    };
+
+    // ---------------------- GENERIC ----------------------
+
+    // codes :: String -> [Int]
+    const codes = s =>
+        s.split('').map(c => c.codePointAt(0));
+
+    // xor :: Int -> Int -> Int
+    const xor = a =>
+        b => (a ^ b)
+
+    // zipWith :: (a -> b -> c) -> [a] -> [b] -> [c]
+    const zipWith = f =>
+        // A list constructed by zipping with a
+        // custom function, rather than with the
+        // default tuple constructor.
+        xs => ys => xs.slice(0).map(
+            (x, i) => f(x)(ys[i])
+        );
+
+    return main()
+})();