Another update from ingydotnet^djgoku

Task/100-doors/JavaScript/100-doors-2.js

@@ -1,6 +1,41 @@
-for (var door = 1; door <= 100; door++) {
-  var sqrt = Math.sqrt(door);
-  if (sqrt === (sqrt | 0)) {
-    console.log("Door %d is open", door);
+(function () {
+  return chain(
+
+    // 100 passes ...
+    rng(0, 99).reduce(function (a, _, i) {
+      return a.slice(0, i).concat(
+        a.slice(i).map(function (v, j) {
+          return (i + j + 1) % (i + 1) ? v : {
+            door: v.door,
+            open: !v.open
+          };
+        })
+      )
+    },
+
+    // 100 closed doors at start
+    Array.apply(null, Array(100)).map(function (x, i) {
+      return {
+        open: false,
+        door: i + 1
+      };
+    })),
+
+    // Filtering by chained function
+    function (door) {
+      return door.open ? [door] : [];
+    }
+  )
+
+  // Monadic bind (chain) for lists
+  function chain(xs, f) {
+    return [].concat.apply([], xs.map(f));
   }
-}
+
+  // range(1, 20) --> [1..20]
+  function rng(m, n) {
+    return Array.apply(null, Array(n - m + 1)).map(function (x, i) {
+      return m + i;
+    });
+  }
+})();