what is ajax function-Front-end Q&A-php.cn

The ajax function refers to the jQuery.ajax() function, which is used to load remote data through background HTTP requests. It is an AJAX technology implementation encapsulated by jQuery. Through this function, we can obtain remote data without refreshing the current page. data on the server.

what is ajax function

The operating environment of this article: Windows 7 system, jquery version 3.2.1, Dell G3 computer.

What is the ajax function?

jQuery.ajax() function detailed explanation

jQuery.ajax() function is used to load through background HTTP requests Remote data.

jQuery.ajax() The function is an implementation of AJAX technology encapsulated by jQuery. Through this function, we can obtain data on the remote server without refreshing the current page.

jQuery.ajax() The function is the underlying AJAX implementation of jQuery. jQuery.get(), jQuery.post(), load(), jQuery.getJSON(), jQuery.getScript() and other functions are all simplified forms of this function (they all call this function, but the parameter settings are different or have some differences). omitted).

This function belongs to the global jQuery object (can also be understood as a static function).

Parameters

Please find the corresponding parameters according to the parameter names defined in the previous syntax section.

Parameters	Description
url	String type URL request string.
settings	Optional/Object type An Object object, each attribute of which is used to specify additional parameter settings required to send a request .

Parameterssettings is an object, jQuery.ajax() can identify the following properties of the object (they are all optional):

accepts --- ObjectType

Default value: Depends At dataType attribute.

The content type request header sent is used to tell the server what type of response the browser can receive from the server.

async --- Boolean type

Default value: true.

Indicates whether it is an asynchronous request. Synchronous requests lock the browser until the remote data is obtained and no other operations can be performed.

beforeSend---Function type

Specify what needs to be executed before the request is sent Callback. This function also has two parameters: one is the jqXHR object, and the other is the current settings object. This is an Ajax event. If the function returns false, this ajax request will be cancelled.

cache---Boolean type

Default value: true(When dataType is 'script' or 'jsonp', the default is false).

Indicates whether to cache URL requests. If set to false it will force the browser not to cache the current URL request. This parameter is only valid for HEAD and GET requests (POST requests themselves will not be cached).

complete---Function/Array type

Specified requestComplete The callback function that needs to be executed after (regardless of success or failure). This function also has two parameters: one is the jqXHR object, and the other is a string representing the request status ('success', 'notmodified', 'error', 'timeout', 'abort' or 'parsererror '). This is an Ajax event.

Starting from jQuery 1.5, the attribute value can be multiple functions in the form of array, and each function will be executed by a callback.

contents---Object Type1.5 New

An object paired with "{string:regular expression}" to determine how jQuery will parse the response, given its content type.

contentType---String Type

Default value: 'application/x- www-form-urlencoded; charset=UTF-8'.

Send data to the server using the specified content encoding type. The W3C's XMLHttpRequest specification stipulates that the charset is always UTF-8. If you change it to another character set, you cannot force the browser to change the character encoding.

context---Object type

Used to set Ajax related callback functions Context object (that is, the this pointer within the function).

converters --- Object Type1.5 New

Default value: {'* text': window.String, 'text html': true, 'text json': jQuery.parseJSON, 'text xml': jQuery.parseXML}.

A data type converter. The value of each converter is a function that returns the converted value of the response.

crossDomain---Boolean Type1.5 New

Default value: Same-domain request is false, cross-domain request is true.

Indicates whether it is a cross-domain request. If you want to force cross-domain requests within the same domain (as in JSONP form), set this to true. This allows server-side redirection to another domain, for example.

data---Any type of data

sent to the server will be automatically forwarded is of string type. If it is a GET request, it will be appended to the URL.

dataFilter---Function type

Specifies the callback for processing the raw data of the response function. This function also has two parameters: one is a string representing the original data of the response, and the other is the dataType attribute string.

dataType---String type

Default value: jQuery smart guess, guess Scope (xml, json, script or html)

Specifies the data type returned. The attribute value can be:

'xml': Returns an XML document that can be processed using jQuery.
'html': Returns an HTML string.
'script': Returns JavaScript code. Results are not cached automatically. Unless the cache parameter is set. Note: When making remote requests (not under the same domain), all POST requests will be converted into GET requests. (Because the DOM script tag will be used to load)
'json': Returns JSON data. JSON data will be parsed using strict syntax (attribute names must be double quoted, and all strings must be double quoted), and an error will be thrown if parsing fails. Starting with jQuery 1.9, responses with empty content will return null or {}.
'jsonp': JSONP format. When calling a function using JSONP format, such as "url?callback=?", jQuery will automatically replace the second ? with the correct function name to execute the callback function.
'text': Returns a plain text string.

error---Function/Array type

Specify the callback function to be executed when the request fails. This function has 3 parameters: jqXHR object, request status string (null, 'timeout', 'error', 'abort' and 'parsererror'), error message string (text description part of the response status, such as 'Not Found' ' or 'Internal Server Error'). This is an Ajax event. Cross-domain scripts and cross-domain JSONP requests will not call this function.

Starting from jQuery 1.5, the attribute value can be multiple functions in the form of array , each function will be executed by a callback.

global---Boolean type

Default value: true.

Indicates whether to trigger the global Ajax event. Setting this value to false will prevent global event handlers from being triggered, such as ajaxStart() and ajaxStop(). It can be used to control various Ajax events.

headers---Object Type1.5 New

default value:{}.

Specify additional request header information in object form. The request header X-Requested-With: XMLHttpRequest will always be added, but you can also modify the default XMLHttpRequest value here. The value in headers can override the request header set in the beforeSend callback function (meaning beforeSend is called first).

$.ajax({
    url: "my.php" ,
    headers: {        "Referer": "http://www.365mini.com" // 有些浏览器不允许修改该请求头
        ,"User-Agent": "newLine" // 有些浏览器不允许修改该请求头
        ,"X-Power": "newLine"
        ,"Accept-Language": "en-US"
    }
});

Copy after login

ifModified---Boolean type

Default value: false .

Allows the current request to obtain new data only when the server data changes (if it has not changed, the browser obtains the data from the cache). It uses HTTP header information Last-Modified to determine. Starting with jQuery 1.4, it also checks the server-specified 'etag' to determine whether the data has been modified.