What does json in ajax mean?

In ajax, json is a data format that can be transferred between different languages. It is a lightweight data exchange format, which is used to exchange data between the browser and the server. JSON is easy to understand and data exchange is faster than XML; it supports arrays, objects, strings, numbers, and values.

The operating environment of this tutorial: windows7 system, javascript version 1.8.5, Dell G3 computer.

Ajax-JSON basic concept

JSON basic concept

JSON full name" "JavaScript Object Notation" is a data format that can be transferred between different languages, a lightweight data exchange format.

In AJAX, it is used to exchange data between the browser and the server. It's easy to understand and data exchange is faster than XML. It supports arrays, objects, strings, numbers and values.

Send a request through AJAX, and the server obtains a JSON data

Comparison between json and xml

xml is also a method of transmitting information .

1. The length of json is very short compared to the xml format.

2. The speed of reading and writing json is faster.

3. json can be parsed directly using the built-in method of javaScript and converted into a javaScript object, which is very convenient.

json syntax rules

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

The name in the name/value pair combination is written in front (in double quotes), the value pair is written in the back (also in double quotes), separated by colons, such as "name":"Guo Jing ".

Different from javaScript object notation, the key values ​​​​of javaScript object notation do not need to be quoted, but the key values ​​​​of json must be quoted.

2. The value of json can be of the following types:

(1) Number (integer or floating point number), such as 123, 1.23

(2) String ( in double quotes)

(3) logical value (true or false)

(4) array (in square brackets)

(5) object (in flower In brackets)

(6) null

3. Typical example of json:

{
  "staff":[
    {"name":"洪七","age":70},
    {"name":"郭靖","age":35}
  ]
}

json parsing

1. json in There are two ways to parse in js: eval and JSON.parse

2. It is very dangerous to use eval in code, especially using it to execute third-party JSON data (which may contain malicious code)

var jsonval= {"staff": [{"name": "洪七","age": 20}, {"name": "洪七2","age": 20}, {"name": "洪七3","age": 20}]}

1) eval()

var jsonbj=('('+jsonval+')');----解析
jssonbj.employees[0].firstName----访问

2) JSON.parse()

var data = JSON.parse(jsonval);---解析
jssonbj.employees[0].firstName----访问

[Related tutorial recommendations: AJAX video tutorial]

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