The relationship between jQuery, ajax, and JSON

In the process of working on projects recently, I have always been unclear about the relationship between jQuery, ajax, and JSON. Therefore, I have a little experience in using it simply, so I The relationship between the three has been studied:

1. jQuery: The following is from Baidu Encyclopedia

jQuery is a fast and concise JavaScript framework, and it is another excellent JavaScript code library after Prototype. (or JavaScript framework).

The purpose of jQuery design is "write Less, Do More", which means writing less code and doing more things. It encapsulates commonly used functional codes in JavaScript, provides a simple JavaScript design pattern, and optimizes HTML document operations, event processing, animation design and Ajax interaction

The core features of jQuery can be summarized as: It has a unique chain syntax and a short and clear multi-functional interface; it has an efficient and flexible CSS selector, and can extend the CSS selector; it has a convenient plug-in extension mechanism and rich plug-ins

From the above content, we can extract the following 2 points:

jQuery is a JavaScript framework

There are many contents in jQuery, Ajax is part of jQuery

2, AJAX

a, what is AJAX?

AJAX = JavaScript and XML (Asynchronous JavaScript and XML)

b. Characteristics of AJAX:

1. Ajax can exchange a small amount of data with the server to update parts asynchronously Web page

2. Asynchronous means that when Ajax performs the operation of exchanging data, other operations can still be performed (common operations such as entering a word on major websites will pop up a lot of content, such as Baidu, Google , Taobao)

c. The core of Ajax technology is the XMLHttpRequest object (referred to as XHR). You can obtain server data by using the XHR object.

d, Ajax format:

type : "",
url : "",
dataType : "json",
data : {
key : value
},
success : function(data) {
},
error : function() {
alert("系统异常");
}
});

type: request method ("POST" or "GET"), the default is "GET"

url: (Default: current page address) The address to which the request is sent.

dataType: The data type expected to be returned by the server. Generally it is json. If not specified, jQuery will automatically intelligently determine

data based on the MIME information of the HTTP package: the data sent to the server. Will be automatically converted to request string format. The GET request will be appended to the URL

success: the callback function after the request is successful. Parameters: Data returned by the server and processed according to the dataType parameter; a string describing the status

error: (Default: automatic judgment (xml or html)) This function is called when the request fails

async: (Default: true) Under default settings, all requests are asynchronous requests. If you need to send a synchronous request, please set this option to false

json value acquisition: the method will directly obtain

public JSONObject chageState(UserInfo userInfo) {
        JSONObject json = new JSONObject();
        return json;
    }

json value passing problem:

can be judged in script After that, pass the desired value. This is a little trick I learned during this project. Because in the initial process, I did not make a judgment and passed the value directly, so I made the judgment in the background. It will be more troublesome; I still don’t know much about this at the beginning, so I learned this little trick when asking my classmates

JSP page dynamic refresh problem:

In the process of working on the project , after adding data, the page needs to be refreshed in real time. This also bothered me for some time. In many cases, if you don’t know how, you should ask and go to Baidu.

This is the end of the simple research on Ajax, because it is used so much now. We will study it later when there are other applications.

3, jQuery

JSON( JavaScript Object Notation, JS object notation) is a lightweight data exchange format;

In the process of ajax value transfer, both data (transmission value) and dataType (return value) are used It’s json

For specific learning about json, please go to: http://www.json.org.cn/index.htm

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