JSON 知识点速查

这是理解和编写 JSON 格式配置文件的快速参考备忘单。

入门

介绍

JSON 是一种基于文本的轻量级开放标准，专为人类可读的数据交换而设计。

  • JSON 代表 JavaScript 对象表示法
  • JSON 易于读写。
  • JSON 是与语言无关的数据交换格式
  • JSON 文件扩展名为 .json
  • JSON Internet 媒体类型为 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
String字符系列
Boolean“true”或“false”
Array有序的值序列
Value字符串、数字、布尔值、空值等
Object键/值对的无序集合
nullNull 或 Empty

字符串

\"双引号 Double quote
\\反斜杠 Backslash
\/正斜杠 Forward slash
\b退格 Backspace
\f换页 Form feed
\n换行 Newline
\r回车 Carriage return
\t标签 Tab
\u后跟四个十六进制数字

示例

{
  "url": "https://jaywcjlove.github.io",
  "msg" : "Hi,\n\"IT开发知识\"",
  "intro": "Share IT开发知识 and cheat sheet for developers."
}

无效字符串

{ "foo": 'bar' }

Have to be delimited by double quotes

数字

类型说明
Integer数字 1-9、0 和正数或负数
Fraction0.3、3.9 等分数
Exponent指数，如 e、e+、e-、E、E+、E

示例

{
  "positive" : 12,
  "negative" : -1,
  "fraction" : 10.25,
  "exponent" : 1.0E+2,
  "zero" : 0
}

无效的数字

{ "foo": 0xFF }

在JSON中，只能使用十进制文字

对象 Objects

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

用逗号分隔的多个键/值对

数组 Arrays

[1, 2, 3, 4, 5]

以 [ 开始并以 ] 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": []
}

二维阵列

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

对象的对象

{
  "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.age39
myObject.otherundefined
myObject[0]undefined

访问嵌套

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.age2
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].genderTypeError: Cannot read...

访问阵列

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

另见