Understand the relevant syntax of json

The relevant syntax of json is very important to js, ​​and this article will explain it.

JSON syntax rules

JSON syntax is a subset of JavaScript object notation syntax.

Data is in name/value pairs

Data is separated by commas

Curly braces hold objects

Square brackets hold arrays

JSON Name/value pair

The writing format of JSON data is: name/value pair.

A name/value pair consists of the field name (in double quotes), followed by a colon, and then the value:

"firstName" : "John"

This is easy to understand, equivalent to this JavaScript statement:

firstName = "John"

JSON value

JSON value can be:

Number ( Integer or floating point number)

String (in double quotes)

Logical value (true or false)

Array (in square brackets)

Object (in curly brackets)

null

JSON object

JSON object in flower Written in brackets:

Objects can contain multiple name/value pairs:

{ "firstName":"John" , "lastName":"Doe" }

This is also easy to understand and is equivalent to this JavaScript statement:

firstName = " John"
lastName = "Doe"

JSON array

JSON array is written in square brackets:

The array can contain multiple objects:

{
"employees": [
{ "firstName":"John" , "lastName":"Doe" },
{ "firstName":"Anna" , "lastName":"Smith" },
{ "firstName":"Peter" , "lastName":"Jones" }
]
}

In the above example, the object "employees" is an array containing three objects. Each object represents a record about a person (with a first and last name).

JSON uses JavaScript syntax

Because JSON uses JavaScript syntax, no additional software is required to process JSON in JavaScript.

With JavaScript, you can Create an array of objects and assign values ​​like this:

Example

var employees = [
{ "firstName":"Bill" , "lastName":"Gates" },
{ "firstName":"George" , "lastName":"Bush" },
{ "firstName":"Thomas" , "lastName": "Carter" }
];

You can access JavaScript object arrays like this The first item:

employees[0].lastName;

The returned content is:

Gates

can be like Modify the data like this:

employees[0].lastName = "Jobs";

In the following chapters, you will learn how to convert JSON text into JavaScript objects.

JSON file

The file type of the JSON file is ".json"

The MIME type of the JSON text is "application/json"

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