如何循环和获取json对象

循环和获取JSON对象的方法

基础概念

JSON（JavaScript Object Notation）是一种轻量级的数据交换格式，易于人阅读和编写，也易于机器解析和生成。它基于JavaScript的一个子集，但独立于语言。

在不同语言中处理JSON对象的方法

JavaScript/TypeScript

// 假设有以下JSON对象
const jsonObj = {
  "name": "John",
  "age": 30,
  "city": "New York",
  "skills": ["JavaScript", "Python", "Java"]
};

// 1. 使用for...in循环
for (const key in jsonObj) {
  if (jsonObj.hasOwnProperty(key)) {
    console.log(`${key}: ${jsonObj[key]}`);
  }
}

// 2. 使用Object.keys()
Object.keys(jsonObj).forEach(key => {
  console.log(`${key}: ${jsonObj[key]}`);
});

// 3. 使用Object.entries()
Object.entries(jsonObj).forEach(([key, value]) => {
  console.log(`${key}: ${value}`);
});

// 处理嵌套对象
const nestedJson = {
  "person": {
    "name": "Alice",
    "address": {
      "street": "123 Main St",
      "city": "Boston"
    }
  }
};

function traverse(obj) {
  for (const key in obj) {
    if (typeof obj[key] === 'object' && obj[key] !== null) {
      traverse(obj[key]);
    } else {
      console.log(`${key}: ${obj[key]}`);
    }
  }
}

traverse(nestedJson);

Python

import json

# 假设有以下JSON字符串
json_str = '{"name": "John", "age": 30, "city": "New York", "skills": ["JavaScript", "Python", "Java"]}'

# 解析JSON字符串为Python字典
data = json.loads(json_str)

# 1. 遍历字典
for key, value in data.items():
    print(f"{key}: {value}")

# 2. 处理嵌套结构
nested_json_str = '{"person": {"name": "Alice", "address": {"street": "123 Main St", "city": "Boston"}}}'
nested_data = json.loads(nested_json_str)

def traverse(data):
    if isinstance(data, dict):
        for key, value in data.items():
            if isinstance(value, (dict, list)):
                traverse(value)
            else:
                print(f"{key}: {value}")
    elif isinstance(data, list):
        for item in data:
            traverse(item)

traverse(nested_data)

Java

import org.json.JSONObject;
import org.json.JSONArray;

public class JsonExample {
    public static void main(String[] args) {
        String jsonStr = "{\"name\":\"John\",\"age\":30,\"city\":\"New York\",\"skills\":[\"JavaScript\",\"Python\",\"Java\"]}";
        
        JSONObject jsonObj = new JSONObject(jsonStr);
        
        // 遍历JSONObject
        for (String key : jsonObj.keySet()) {
            Object value = jsonObj.get(key);
            System.out.println(key + ": " + value);
        }
        
        // 处理嵌套结构
        String nestedJsonStr = "{\"person\":{\"name\":\"Alice\",\"address\":{\"street\":\"123 Main St\",\"city\":\"Boston\"}}}";
        JSONObject nestedJson = new JSONObject(nestedJsonStr);
        
        traverse(nestedJson);
    }
    
    public static void traverse(Object obj) {
        if (obj instanceof JSONObject) {
            JSONObject jsonObj = (JSONObject) obj;
            for (String key : jsonObj.keySet()) {
                Object value = jsonObj.get(key);
                if (value instanceof JSONObject || value instanceof JSONArray) {
                    traverse(value);
                } else {
                    System.out.println(key + ": " + value);
                }
            }
        } else if (obj instanceof JSONArray) {
            JSONArray jsonArray = (JSONArray) obj;
            for (int i = 0; i < jsonArray.length(); i++) {
                traverse(jsonArray.get(i));
            }
        }
    }
}