JSON 初学者完整指南 |凯蒂博客

JSON (JavaScript Object Notation) is the universal language of data exchange on the web. Whether you're building APIs, storing configuration files, or communicating between services, understanding JSON is essential for any developer. This comprehensive guide takes you from the basics to advanced concepts.

什么是 JSON？

JSON is a lightweight, text-based data interchange format. Despite "JavaScript" in the name, JSON is language-independent and supported by virtually every programming language. It was derived from JavaScript object syntax but has become the de facto standard for data exchange.

💡 Fun Fact: JSON was popularized by Douglas Crockford in the early 2000s. It's now defined by two standards: RFC 8259 and ECMA-404. The format is so simple that the entire specification fits on a business card.

JSON 语法：基础知识

JSON is built on two structures:

Objects: Collections of key-value pairs enclosed in curly braces {}
Arrays: Ordered lists of values enclosed in square brackets []

一个简单的 JSON 对象

                {

                  "name": "John Doe",

                  "age": 30,

                  "isActive": true,

                  "email": "[email protected]"

                }

JSON 数据类型

JSON supports six data types:

Type	Example	Description
String	`"Hello World"`	Text enclosed in double quotes
Number	`42`, `3.14`, `-17`	Integer or floating-point
Boolean	`true`, `false`	Logical values (lowercase)
Null	`null`	Empty or absent value
Object	`{"key": "value"}`	Unordered key-value pairs
Array	`[1, 2, 3]`	Ordered list of values

嵌套结构

JSON's power comes from nesting objects and arrays:

                {

                  "user": {

                    "id": 12345,

                    "profile": {

                      "firstName": "Jane",

                      "lastName": "Smith"

                    },

                    "tags": ["developer", "designer"]

                  }

                }

常见的 JSON 错误

⚠️ JSON is Strict: Unlike JavaScript objects, JSON requires exact syntax. A single error will cause parsing to fail completely.

1. 尾随逗号

// ❌ Invalid - trailing comma after last item

                { "name": "John", "age": 30, }

// ✅ Valid

                { "name": "John", "age": 30 }

2. 单引号

// ❌ Invalid - JSON requires double quotes

                { 'name': 'John' }

// ✅ Valid

                { "name": "John" }

3. 不带引号的键

// ❌ Invalid - keys must be quoted

                { name: "John" }

// ✅ Valid

                { "name": "John" }

4. 评论

// ❌ Invalid - JSON doesn't support comments

                {

                  "name": "John" // This is a name

                }

// ✅ JSON simply doesn't allow comments

在 JavaScript 中使用 JSON

解析 JSON（字符串 → 对象）

                const jsonString = '{"name": "John", "age": 30}';

                const user = JSON.parse(jsonString);

                console.log(user.name); // "John"

                console.log(user.age); // 30

字符串化（对象 → 字符串）

                const user = { name: "John", age: 30 };

                const jsonString = JSON.stringify(user);

                console.log(jsonString);

// '{"name":"John","age":30}'

漂亮的印刷

                const user = { name: "John", age: 30 };

// Third parameter = indentation spaces

                const pretty = JSON.stringify(user, null, 2);

                console.log(pretty);

// {

// "name": "John",

// "age": 30

// }

✅ 专业提示：安全解析

Always wrap JSON.parse() in try-catch to handle invalid JSON gracefully instead of crashing your application.

在 Python 中使用 JSON

                import json

# Parsing JSON

                json_string = '{"name": "John", "age": 30}'

                user = json.loads(json_string)

                print(user["name"]) # John

# Creating JSON

                user_dict = {"name": "Jane", "age": 25}

                json_output = json.dumps(user_dict, indent=2)

                print(json_output)

JSON 与 XML：何时分别使用

Aspect	JSON	XML
Readability	More readable for humans	More verbose
File Size	Smaller	Larger (more markup)
Parsing Speed	Faster	Slower
Data Types	Native types (numbers, booleans)	Everything is a string
Comments	Not supported	Supported
Namespaces	Not supported	Supported
Best For	APIs, web apps, config files	Documents, complex schemas

真实的 JSON 示例

API响应

                {

                  "status": "success",

                  "data": {

                    "users": [

                      { "id": 1,
                "name": "Alice" },

                      { "id": 2,
                "name": "Bob" }

                    ],

                    "total": 2

                  }

                }

配置文件（package.json）

                {

                  "name": "my-project",

                  "version": "1.0.0",

                  "dependencies": {

                    "express": "^4.18.0",

                    "lodash": "^4.17.21"

                  }

                }

最佳实践

Use descriptive keys: "firstName" is better than "fn"
Be consistent with naming: Choose camelCase or snake_case and stick with it
Validate before parsing: Always validate JSON from external sources
Handle null values explicitly: Don't omit keys—use null for empty values
Use arrays for lists: Even if there's currently only one item
Keep nesting reasonable: Deeply nested JSON is hard to work with

🔧 需要格式化或验证 JSON？

Use our free JSON Formatter tool to beautify, validate, and minify JSON instantly.

打开 JSON 格式化程序 →

结论

JSON's simplicity is its strength. With just objects, arrays, and six data types, you can represent virtually any data structure. Master the basics covered here, avoid the common pitfalls, and you'll be working with JSON like a pro.

Remember: when in doubt, validate your JSON with a tool before debugging your code. Nine times out of ten, the issue is a syntax error—usually a missing comma or quote.

📋 JSON 初学者完整指南