Ajax tutorial,

Ajax tutorial,

What Is AJAX?

AJAX is a technology that updates some webpages without the need to reload the entire webpage. By performing a small amount of data exchange with the server in the background, AJAX can implement asynchronous updates on webpages.

 

What are common AJAX parameters?

Async

Type: Boolean

Default Value: true. By default, all requests are asynchronous requests. To send a synchronization request, set this option to false.

 

BeforeSend (XHR)

Type: Function

If false is returned, the ajax request can be canceled.

 

Cache

Type: Boolean

Default Value: true. If script ype is set to script or jsonp, the default value is false. If this parameter is set to false, the page is not cached.

 

Complete (XHR, TS)

Type: Function

Callback Function after the request is complete (called after the request is successful or fails ).

 

ContentType

Type: String

Default Value: "application/x-www-form-urlencoded ". Content Encoding type when sending information to the server. The default value is applicable in most cases.

 

Context

Type: Object

This object is used to set the context of Ajax-related callback functions. That is to say, let this in the callback function point to this object (if this parameter is not set, this points to the options parameter passed when this AJAX request is called ). For example, if you specify a DOM element as the context parameter, the context of the success callback function is set to this DOM element.

Like this:

$. Ajax ({url: "test.html", context: document. body, success: function (){

$ (This). addClass ("done ");

}});

 

Data

Type: String

The data sent to the server. Will be automatically converted to the request string format. The GET request will be appended to the URL. View the description of the processData option to disable automatic conversion. It must be in Key/Value format. If it is an array, jQuery automatically corresponds to the same name for different values. For example, {foo: ["bar1", "bar2"]} is converted to '& foo = bar1 & foo = bar2 '.

 

DataFilter

Type: Function

A preprocessing function for the original data returned by Ajax. Two parameters are provided: data is the original data returned by Ajax, and type is the dataType parameter provided when jQuery. ajax is called. The value returned by the function will be further processed by jQuery.

 

DataType

Type: String

Expected data type returned by the server. If this parameter is not specified, jQuery automatically determines Based on the MIME information of the HTTP package. For example, the xml mime type is recognized as XML. In 1.4, JSON will generate a JavaScript Object, and script will execute this script. The data returned by the server is parsed based on this value and passed to the callback function. Available value:

"Xml": returns an XML document, which can be processed by jQuery.

"Html": returns plain text HTML information. The script tag is executed when the dom is inserted.

"Script": returns plain text JavaScript code. Results are not automatically cached. Unless the "cache" parameter is set. Note: During remote requests (not in the same domain), all POST requests are converted to GET requests. (Because the script tag of DOM will be used for loading)

"Json": Return JSON data.

"Jsonp": JSONP format. When calling a function in the form of JSONP, such as "myurl? Callback =? "Will jQuery be replaced automatically? For the correct function name to execute the callback function.

"Text": returns a plain text string.

 

Error

Type: Function

Default Value: Automatic judgment (xml or html ). This function is called when the request fails.

There are three parameters: XMLHttpRequest object, error message, and (optional) caught exception object.

If an error occurs, in addition to null, the error message (the second parameter) may also be "timeout", "error", "notmodified", and "parsererror ".

 

Global

Type: Boolean

Whether to trigger a global AJAX event. Default Value: true. Setting false does not trigger global AJAX events. For example, ajaxStart or ajaxStop can be used to control different Ajax events.

 

IfModified

Type: Boolean

Obtain New data only when the server data changes. Default Value: false. Use the Last-Modified header information of the HTTP packet to determine. In jQuery 1.4, it also checks the 'etag' specified by the server to confirm that the data has not been modified.

 

Jsonp

Type: String

Rewrite the name of the callback function in a jsonp request. This value is used to replace "callback =? "The" callback "section of the URL parameter in this GET or POST request, for example, {jsonp: 'onjsonpload'} causes" onJsonPLoad =? "To the server.

 

JsonpCallback

Type: String

Specify a callback function name for the jsonp request. This value is used to replace the random function name automatically generated by jQuery. This function is mainly used to make jQuery generate a unique function name, which makes it easier to manage requests and conveniently provide callback functions and error handling. You can also specify the callback function name when you want the browser to cache the GET request.

 

Password

Type: String

Password used to respond to HTTP access authentication requests

 

ProcessData

Type: Boolean

Default Value: true. By default, data transmitted through the data option is converted into a query string if it is an object (technically, as long as it is not a string, with the default content type "application/x-www-form-urlencoded ". If you want to send the DOM tree information or other information that does not want to be converted, set it to false.

 

ScriptCharset

Type: String

Only when the ype is "jsonp" or "script" and the type is "GET" Can the charset be forcibly modified. It is usually used only when the local and remote content encoding is different.

 

Success

Type: Function

The callback function after the request is successful.

Parameter: the data that is returned by the server and processed according to the dataType parameter; a string that describes the status.

 

Traditional

Type: Boolean

If you want to serialize data in a traditional way, set it to true. See the jQuery. param method below the tool category.

 

Timeout

Type: Number

Set the request timeout (in milliseconds ). This setting overwrites the global setting.

 

Type

Type: String

Default Value: "GET "). Request Method ("POST" or "GET"). The default value is "GET ". Note: Other HTTP request methods, such as PUT and DELETE, can also be used, but are only supported by some browsers.

 

Url

Type: String

Default Value: the current page address. The address where the request is sent.

 

Username

Type: String

The username used to respond to the HTTP access authentication request.

 

Xhr

Type: Function

You need to return an XMLHttpRequest object. ActiveXObject in IE and XMLHttpRequest in other cases by default. Used to override or provide an enhanced XMLHttpRequest object.