Added 3 JavaScript maybe implementations

Author: MarcusAurelius

JavaScript/maybe.js

@@ -0,0 +1,14 @@
+function Maybe(x) {
+  this.x = x;
+}
+
+Maybe.prototype.map = function(fn) {
+  if (this.x && fn) {
+    return new Maybe(fn(this.x));
+  } else {
+    return new Maybe(null);
+  }
+}
+
+new Maybe(5).map(x => x * 2).map(console.log);
+new Maybe(null).map(x => x * 2).map(console.log);

JavaScript/maybe2.js

@@ -0,0 +1,12 @@
+function Maybe(x) {
+  return function(fn) {
+    if (x && fn) {
+      return Maybe(fn(x));
+    } else {
+      return Maybe(null);
+    }
+  };
+}
+
+Maybe(5)(x => x * 2)(console.log);
+Maybe(null)(x => x * 2)(console.log);

JavaScript/maybe3.js

@@ -0,0 +1,23 @@
+function Maybe(x) {
+  this.x = x;
+}
+
+Maybe.prototype.map = function(fn) {
+  if (this.x && fn) {
+    return new Maybe(fn(this.x));
+  } else {
+    return new Maybe(null);
+  }
+}
+
+Maybe.prototype.ap = function(maybe) {
+  if (maybe) {
+    return maybe.map(this.x);
+  } else {
+    return new Maybe(null);
+  }
+}
+
+let a = new Maybe(5);
+let b = new Maybe(x => x * 2);
+let c = b.ap(a).map(console.log);