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In this article, the editor introduces "what is the grammar of JSON" in detail, the content is detailed, the steps are clear, and the details are handled properly. I hope this article "what is the grammar of JSON" can help you solve your doubts.

Json is a data format, not a programming language.

Json is a lightweight data format that simplifies the workload of representing complex data structures.

1. Grammar

① json strings must be in double quotation marks

② does not declare variables

③ has no trailing semicolon

Attribute names in ④ json objects must be in double quotation marks

The syntax of json can represent three types of values

Simple values: using the same syntax as js, you can represent strings, numeric values, Boolean values, and null in json. (undefined is not supported)

"hello world"

Object:

{

"name": "Ewall"

"age": 21

}

Array:

[25, "ewall", true]

2. JSON object

Two methods: stringfy (): serialize the js object into a json string

Parse (): parses json strings to native js values

Var person= {

Name: "Ewall"

Friends: ["joe", "frank"]

Edition:3

Year:2017

}

Var jsonText=JSON.stringify (person)

Console.log (jsonText)

3. The specific usage of JSON.stringfy ()

This method can pass in three parameters, the first is the object to be serialized, the second is a filter (either an array or a function), and the third is an option indicating whether to retain indentation in the JSON string.

① when the filter is an array, the result returned by this method will contain only the properties listed in the array

Var person= {

Name: "Ewall"

Friends: ["joe", "frank"]

Edition:3

Year:2017

}

Var jsonText=JSON.stringify (person, ["name", "year"])

Console.log (jsonText); / / {"name": "Ewall", "year": 2017}

② treats the filter as a function. The incoming function takes two parameters, the property name and the property value, and you can know how to handle the properties in the object to be serialized based on the property name.

Var person= {

Name: "Ewall"

Friends: ["joe", "frank"]

Edition:3

Year:2017

}

Var jsonText=JSON.stringify (person,function (key,value) {

Switch (key) {

Case "friends":

Return value.join (,)

Case "year":

Return undefined; / / Delete this attribute by returning undefined

Default:

Return value

}

})

Console.log (jsonText); / / {"name": "Ewall", "friends": "joe,frank", "edition": 3}

4. The specific usage of the JSON.parse () method

Receive two parameters: the first is the object to be serialized, and the second is a restore function.

The restore function is often used when converting a date string to a Date object.

Var person= {

Name: "Ewall"

Friends: ["joe", "frank"]

Edition:3

Year:2017

ReleaseDate:new Date ()

}

Var jsonText=JSON.stringify (person)

Console.log (jsonText)

Var bookCopy=JSON.parse (jsonText,function (key,value) {

If (key== "releaseDate") {

Return new Date (value); / / create a new Date object based on the corresponding json value

} else {

Return value

}

})

Console.log (bookCopy.releaseDate)

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