maybe.js

Maybe = function(value) {
  var Nothing = {};

  var Something = function(value) { 
    return function() {
      return value; 
    };
  };

  if (typeof value === 'undefined' || value === null)
    return Nothing;

  return Something(value);
};

Maybe(null) == Nothing; // true
typeof Maybe(null); // 'object'

Maybe('foo') == Nothing; // false
Maybe('foo')(); // 'foo'
typeof Maybe('foo'); // 'function'

function just(x){ return {just: x}; }
var nothing = {nothing: null};
function maybe(d, f, m){
if('nothing' in m){
return d;
}
elseif('just' in m){
return f(m.just);
}
else{
throw new Exception("invalid maybe value");
}
}

function >>=(m, f){
if('null' in m){
return nothing;
}
elseif('just' in m){
return f(m.just);
}
else{
throw new Exception("invalid maybe value");
}
}