JavaScript optional result values

optional.js

var optional = (function() {
    var noneInternal = function() {};
    noneInternal.prototype.isNone = function() { return true; };
    noneInternal.prototype.isSome =  function() { return false; };
    noneInternal.prototype.bind = function(fun) { return none(); }; 
 
    var none = function() {
        return new noneInternal(); // make fiddling less probable
    };
 
    someIsNone = function() { return false; };
    someIsSome =  function() { return true; };
    someBind = function(fun) { 
        var ret = fun(this());
        return create(ret);
    };
    var some = function(value) {
        var result = function() {
            return value;
        };
        result.isNone = someIsNone;
        result.isSome =  someIsSome;
        result.bind = someBind;
        return result;
    }
 
    var create = function(value) {
        if (value != null) {
            return some(value);
        }
        return none(); 
 
    };
 
    return {
        create: create,
        none: none,
        some: some 
    };
})();

test-optional.js

    module("optional");
 
test("null should yield none", function() {
    var o = optional.create(null);
    ok(o.isNone());
    ok(!o.isSome());
    o = optional.none();
    ok(o.isNone());
    ok(!o.isSome());
});
 
test("null should throw if called", function() {
    throws(
        function() {
            var o = optional.none();
            o();
        });
});
 
test("null bind should always return none", function() {
    var o = optional.none();
    var o1 = o.bind(function(value) {
        return optional.create("not called");
    });
    ok(o1.isNone());
});
 
test("value should yield some", function() {
    var o = optional.create("hello");
    ok(o.isSome());
    ok(!o.isNone());
});
 
test("invoking some should return value", function() {
    var o = optional.some("hamsdi");
    equal(o(), "hamsdi");
});
 
test("binding some should be invoked", function() {
    var o = optional.some("hamsdi");
    o.bind(function(value) {
        equal(value, "hamsdi");
    });
});
 
test("non null result of binding should be itself be some", function() {
   var o1 = optional.some("hamsdi");
    var o2 = o1.bind(function(value) {
        equal(value, "hamsdi");
        return "bamsdi";
    }); 
    ok(o2.isSome());
});
 
test("null result of binding should be itself be none", function() {
   var o1 = optional.some("hamsdi");
    var o2 = o1.bind(function(value) {
        equal(value, "hamsdi");
        return null;
    }); 
    ok(o2.isNone());
});
 
test("binding cascade", function() {
    var my = optional.create("hamsdi");
    var r = my.bind(function(value) {
        return value + " bamsdi";
    }).bind(function(value) {
        return "Hello " + value;
    }).bind(function(value) {
        return value + "!";
    });
 
    equal(r(), "Hello hamsdi bamsdi!");
});