js json 数组 添加

{
"employees": [
{ "firstName":"John" , "lastName":"Doe" },
{ "firstName":"Anna" , "lastName":"Smith" },
{ "firstName":"Peter" , "lastName":"Jones" }
]
}

            var json = {"employees": []};
            var jsonitem = { "firstName":"Peter" , "lastName":"Jones" };
            var jsonitem2 = { "firstName":"John" , "lastName":"Doe" };
            var jsonitem3 = { "firstName":"Anna" , "lastName":"Smith" };
            json.employees.push(jsonitem);
            json.employees.push(jsonitem2);
            json.employees.push(jsonitem3);
            alert(json.employees[2].firstName);