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JSON

这是一个用于理解和编写 JSON 格式配置文件的快速参考备忘单。

#入门

#简介

JSON 是一种轻量级的基于文本的开放标准，专为人类可读的数据交换而设计。

  • JSON 代表 JavaScript Object Notation
  • JSON 易于阅读和编写。
  • JSON 是一种与语言无关的数据交换格式
  • JSON 文件扩展名是 .json
  • JSON 互联网媒体类型是 application/json

#示例

{
  "name": "Jason",
  "age": 39,
  "height": 1.92,
  "gender": "M",
  "salary": 70000,
  "married": true,
  "children": [
    { "name": "Tom", "age": 9, "gender": "M" },
    { "name": "Ava", "age": 7, "gender": "F" }
  ]
}

#类型

类型 描述
Number 双精度浮点数
String 字符序列
Boolean true 或 false
Array 值的有序序列
Value 字符串、数字、布尔值、null 等
Object 键/值对的无序集合
null Null 或空

#字符串
\" 双引号
\\ 反斜杠
\/ 正斜杠
\b 退格
\f 换页符
\n 换行符
\r 回车符
\t 制表符
\u 后跟四个十六进制数字

#示例

{
  "url": "https://r3f.cn",
  "msg": "Hi,\n\"r3f.cn\"",
  "intro": "Share quick reference and cheat sheet for developers."
}

#无效字符串

{ "foo": "bar" }

必须用双引号分隔

#数字

类型 描述
Integer 数字 1-9、0 以及正数或负数
Fraction 小数，如 0.3、3.9
Exponent 指数，如 e、e+、e-、E、E+、E

#示例

{
  "positive": 12,
  "negative": -1,
  "fraction": 10.25,
  "exponent": 1.0e2,
  "zero": 0
}

#无效数字

{ "foo": 0xff }

在 JSON 中，您只能使用十进制字面量

#对象

{
  "color": "Purple",
  "id": "210",
  "composition": {
    "R": 70,
    "G": 39,
    "B": 89
  },
  "empty_object": {}
}

多个键/值对，用逗号分隔

#数组

[1, 2, 3, 4, 5]

以 [ 开始，以 ] 结束

#对象数组

{
  "children": [
    { "name": "Jimmy Smith", "age": 15 },
    { "name": "Sammy Sosa", "age": 12 }
  ]
}

#数组对象

{
  "attributes": ["a1", "a2"],
  "methods": ["getter", "setter"],
  "empty_array": []
}

#二维数组

{
  "my_sequences": [
    [1, 2, 3],
    [4, 5, 6],
    [7, 8, 9, 0],
    [10, 11]
  ]
}

#对象嵌套对象

{
  "Mark McGwire": {
    "hr": 65,
    "avg": 0.278
  },
  "Sammy Sosa": {
    "hr": 63,
    "avg": 0.288
  }
}

#嵌套

{
  "Jack": {
    "id": 1,
    "name": "Franc",
    "salary": 25000,
    "hobby": ["a", "b"],
    "location": {
      "country": "A",
      "city": "A-A"
    }
  }
}

#在 JavaScript 中访问 JSON

#访问对象

let myObject = {
  name: "Jason",
  last: "Doe",
  age: 39,
  gender: "M",
  salary: 70000,
  married: true,
};
myObject.name "Jason"
myObject["name"] "Jason"
myObject.age 39
myObject.other undefined
myObject[0] undefined

#访问嵌套对象

let myObject = {
  ref: {
    name: 0,
    last: 1,
    age: 2,
    gender: 3,
    salary: 4,
    married: 5,
  },
  jdoe: ["Jason", "Doe", 39, "M", 70000, true],
  jsmith: ["Tom", "Smith", 42, "F", 80000, true],
};
myObject.ref.age 2
myObject["ref"]["age"] 2
myObject.jdoe ["Jason", "Doe", 39 ...]
myObject.jsmith[3] "F"
myObject[1] undefined

#访问对象数组

let myArray = [
  {
    name: "Jason",
    last: "Doe",
    age: 39,
    gender: "M",
    salary: 70000,
    married: true,
  },
  {
    name: "Tom",
    last: "Smith",
    age: 42,
    gender: "F",
    salary: 80000,
    married: true,
  },
  {
    name: "Amy",
    last: "Burnquist",
    age: 29,
    gender: "F",
    salary: 60000,
    married: false,
  },
];
myArray[0] {"name": "Jason", ...}
myArray[1].name "Tom"
myArray[1][2] 42
myArray[3] undefined
myArray[3].gender TypeError: Cannot read...

#访问数组

let myArray = ["Jason", "Doe", 39, "M", 70000, true];
myArray[1] "Doe"
myArray[5] true
myArray[6] undefined

#另请参阅