【Javascript】多层json对象，根据key获取value

function getvaluebykey (data, field) {
    for (let key in data) {
        if (key === field) {
            return data[key];
        }
        if (typeof(data[key]) === 'object' && data[key].length === undefined) {
            return getvaluebykey(data[key], textfield);
        } 
    }
}

var jsonobj = {
    "中国": {
        "北京": [
            "朝阳"
        ],
        "广州": [
            "天河"
        ]
    },
    "美国": {},
    "英国": [
        "爱尔兰"
    ]
}

var result = getvaluebykey(jsonobj, '广州');
console.log(result);  //['天河']