2016 Update

Task/Find-the-last-Sunday-of-each-month/JavaScript/find-the-last-sunday-of-each-month-2.js

@@ -0,0 +1,73 @@
+(function () {
+    'use strict';
+
+    // lastSundaysOfYear :: Int -> [Date]
+    function lastSundaysOfYear(y) {
+        return lastWeekDaysOfYear(y, days.sunday);
+    }
+
+    // lastWeekDaysOfYear :: Int -> Int -> [Date]
+    function lastWeekDaysOfYear(y, iWeekDay) {
+        return [
+                31,
+                0 === y % 4 && 0 !== y % 100 || 0 === y % 400 ? 29 : 28,
+                31, 30, 31, 30, 31, 31, 30, 31, 30, 31
+            ]
+            .map(function (d, m) {
+                var dte = new Date(Date.UTC(y, m, d));
+
+                return new Date(Date.UTC(
+                    y, m, d - (
+                        (dte.getDay() + (7 - iWeekDay)) % 7
+                    )
+                ));
+            });
+    }
+
+    // isoDateString :: Date -> String
+    function isoDateString(dte) {
+        return dte.toISOString()
+            .substr(0, 10);
+    }
+
+    // range :: Int -> Int -> [Int]
+    function range(m, n) {
+        return Array.apply(null, Array(n - m + 1))
+            .map(function (x, i) {
+                return m + i;
+            });
+    }
+
+    // transpose :: [[a]] -> [[a]]
+    function transpose(lst) {
+        return lst[0].map(function (_, iCol) {
+            return lst.map(function (row) {
+                return row[iCol];
+            });
+        });
+    }
+
+    var days = {
+        sunday: 0,
+        monday: 1,
+        tuesday: 2,
+        wednesday: 3,
+        thursday: 4,
+        friday: 5,
+        saturday: 6
+    }
+
+    // TEST
+
+    return transpose(
+            range(2012, 2016)
+            .map(lastSundaysOfYear)
+        )
+        .map(function (row) {
+            return row
+                .map(isoDateString)
+                .join('\t');
+        })
+        .join('\n');
+
+})();