maybe.js

function maybe(x) {
   return {
       bind: function(f) { 
	   if(x == null) {
	       return null;
	   } else {
	       return f(x);
	   }
       },
       getDefault: function(y) {
	   return y ? x == null : x
       }
   }
}

function lookup(key, obj) {
    return function(obj) {
	return maybe(obj[key]);
    };
};

function getNested(obj) {
    var keys = [].slice.call(arguments, 1);
    return [].reduce.call(keys,
	function(m, key) {
	    return m.bind(lookup(key));
	},
	maybe(obj)
    );
}

obj = {"foo": {"bar": "baz"}};

console.log(
    maybe(obj.foo).bind(lookup("bar")).getDefault(null)
);

console.log(
    maybe(obj.foo).bind(lookup("bing")).getDefault(null)
);

console.log(getNested(obj, "foo", "bar").getDefault(null));
console.log(getNested(obj, "foo", "bing").getDefault(null));