【转】如何遍历json数据

var value = {
    "china":{
        "hangzhou":{"item":"1"},
        "shanghai":{"item":"2"},
        "chengdu":{"item":"3"}
    },
    "America":{
        "aa":{"item":"1"},
        "bb":{"item":"2"}    
    },
    "Spain":{
        "dd":{"item":"1"},
        "ee":{"item":"2"},
        "ff":{"item":"3"}    
    }
};

for(var countryObj in value)
{
    document.write(countryObj + ":<br />")
    //没用的for(var cityObj in value.countryObj)
    for(var cityObj in value[countryObj])
    {
        document.write('&nbsp;&nbsp;&nbsp;&nbsp;' + cityObj + "<br />");
        for(var itemObj in value[countryObj][cityObj])
        {
            document.write("&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;"+ itemObj + value[countryObj][cityObj][itemObj] +"<br />")    
        }
    }    
}