2016 Update

Task/Symmetric-difference/JavaScript/symmetric-difference-3.js

@@ -0,0 +1,66 @@
+((a, b) => {
+    'use strict';
+
+
+    let // UNION AND DIFFERENCE
+
+    // union :: [a] -> [a] -> [a]
+        union = (xs, ys) => unionBy((a, b) => a === b, xs, ys),
+
+        // difference :: [a] -> [a] -> [a]
+        difference = (xs, ys) =>
+            ys.reduce((a, y) =>
+                a.indexOf(y) !== -1 ? (
+                    delete_(y, a)
+                ) : a.concat(y), xs),
+
+
+
+        // GENERAL PRIMITIVES
+
+        // unionBy :: (a -> a -> Bool) -> [a] -> [a] -> [a]
+        unionBy = (f, xs, ys) => {
+            let sx = nubBy(f, xs),
+                sy = nubBy(f, ys);
+
+            return sx.concat(
+                sx
+                .reduce(
+                    (a, x) => deleteBy(f, x, a),
+                    sy
+                )
+            )
+        },
+
+        // deleteBy :: (a -> a -> Bool) -> a -> [a] -> [a]
+        deleteBy = (f, x, xs) =>
+            xs.reduce((a, y) => f(x, y) ? a : a.concat(y), []),
+
+        // delete_  :: a -> [a] -> [a]
+        delete_ = (x, xs) =>
+            deleteBy((a, b) => a === b, x, xs),
+
+        // nubBy :: (a -> a -> Bool) -> [a] -> [a]
+        nubBy = (f, xs) => {
+            let x = (xs.length ? xs[0] : undefined);
+
+            return x !== undefined ? [x].concat(
+                nubBy(f, xs.slice(1)
+                    .filter(y => !f(x, y))
+                )
+            ) : [];
+        };
+
+
+
+    // 'SYMMETRIC DIFFERENCE'
+
+    return union(
+        difference(a, b),
+        difference(b, a)
+    );
+
+})(
+    ["John", "Serena", "Bob", "Mary", "Serena"],
+    ["Jim", "Mary", "John", "Jim", "Bob"]
+);

Task/Symmetric-difference/JavaScript/symmetric-difference-4.js

@@ -0,0 +1 @@
+["Serena", "Jim"]