Пример замыканий

        function addProtectedVar(object, name, validator){
            if (! typeof(object) == "object")
                throw new Error("Object required for the first argument!");
            if (name.length == 0)
                throw new Error("Set name of variable to the second argument!");
            if (validator && (typeof(validator)!="function"))
                throw new Error("Third argument must be a function!");
            if (validator && validator.length != 1)
                throw new Error("Validator function must receive 1 argument!");
            camel_name = name.charAt(0).toUpperCase() + name.substr(1);
            if (object.hasOwnProperty('set' + camel_name) || object.hasOwnProperty('get' + camel_name))
                throw new Error("Object already has method/property set" + camel_name + ' or get' + camel_name);
            functions = (function(name, validator){
                var property;
                var variable_name = name;
                return {
                    get:function(){
                        return property;
                    },
                    set:function(value){
                        if (validator){
                            if (validator(value))
                                property = value;
                            else
                                throw new Error("Wrong value for \"" + variable_name + "\" property!");
                        }else{
                            property = value;
                        }
                    }
                };
            })(name,validator);
            object["get" + camel_name] = functions["get"];
            object["set" + camel_name] = functions["set"];
        }

        var object = {x:1, y:2};
        try{
            addProtectedVar(object, 'secret', function(val){return val > 0});
            addProtectedVar(object, 'secret2', function(val){return (val % 2) == 0});
            addProtectedVar(object, 'secret3', function(val){return (val % 2) == 0});
            object.setSecret(12);
            object.getSecret(); // 12
            object.setSecret2(4);
        }catch(e){
            console.error(e);
        }