空手道:有没有办法从示例变量中获取JSON对象键的长度？

import json

json_str = '{"name": "John", "age": 30, "city": "New York"}'
json_obj = json.loads(json_str)

key_length = len(json_obj.keys())
print(key_length)

3

import org.json.JSONObject;

String jsonStr = "{\"name\": \"John\", \"age\": 30, \"city\": \"New York\"}";
JSONObject jsonObj = new JSONObject(jsonStr);

int keyLength = jsonObj.length();
System.out.println(keyLength);

3

var jsonObj = {"name": "John", "age": 30, "city": "New York"};

var keyLength = Object.keys(jsonObj).length;
console.log(keyLength);

3