jquery uses Ajax Cross-domain requests to fetch data _ajax related

Cross-Domain is a question that I often ask in everyday interviews, the word's frequency is not low in the front-end world, mainly because of security restrictions (homology policy, that is, JavaScript or cookies can only access the content under the same domain), because we will inevitably need to do cross-domain operations in our daily project development. So Cross-domain ability is also regarded as one of the basic skills of front-end engineers.

var WebMethod = "Http://localhost:54473/Service1.asmx/HelloWorld"; 
JQuery.support.cors = true;
Didn't add this sentence always hint no transport, I didn't go to deep thought.
  $.ajax
  ({
   
   type: POST,
   contentType: "application/x-www-form-urlencoded",
   dataType: "html",
   URL: "http:// Www.*****.com ",//Here is the URL
   success:function (data) {alert (data);},
   timeout:30000, 
   error:function ( XMLHttpRequest, Textstatus, Errorthrown) {
   alert (errorthrown);
   }
  });

Parameters

Options

Type: Object

Optional. AJAX request settings. All options are optional.

Async

Type: Boolean

Default value: True. All requests are asynchronous requests under the default settings. If you need to send a sync request, set this option to false.

Note that the synchronization request will lock the browser and the user's other actions must wait for the request to complete before it can be executed.

Beforesend (XHR)

Type: Function

You can modify the functions of the XMLHttpRequest object before sending the request, such as adding a custom HTTP header.

The XMLHttpRequest object is the only parameter.

This is an Ajax event. If you return False, you can cancel this Ajax request.

Cache

Type: Boolean

Default value: False when True,datatype is script and Jsonp. Set to False to not cache this page.

JQuery 1.2 new features.

Complete (XHR, TS)

Type: Function

The callback function (called after the request succeeds or fails) after the request completes.

Parameters: XMLHttpRequest object and a string that describes the request type.

This is an Ajax event.

ContentType

Type: String

Default value: "Application/x-www-form-urlencoded". Content encoding type when sending information to the server.

Default values are appropriate for most situations. If you explicitly pass a content-type to $.ajax () then it will definitely be sent to the server (even if there is no data to send).

Context

Type: Object

This object is used to set the context of Ajax-related callback functions. That is, let this point in the callback function refer to this object (if this argument is not set, this will point to the options argument passed when the AJAX request is invoked). For example, a DOM element is specified as the context parameter, so that the success callback function is set to this DOM element.

Just like this:

$.ajax ({url: "test.html", Context:document.body, Success:function () {
  $ (this). AddClass ("Done");
  });

Data

Type: String

Data sent to the server. is automatically converted to the request string format. The GET request is appended to the URL. View the ProcessData option description to prevent this automatic conversion. Must be in the Key/value format. If you are an array, JQuery will automatically correspond to the same name for different values. such as {foo:["bar1", "Bar2"]} is converted to ' &foo=bar1&foo=bar2 '.

Datafilter

Type: Function

A function to preprocess the raw data returned by Ajax. Provides data and type two parameters: Data is the original source returned by Ajax, and type is the DataType parameter provided when calling Jquery.ajax. The value returned by the function will be further processed by JQuery.

DataType

Type: String

The type of data expected to be returned by the server. If not specified, JQuery will automatically intelligently judge against HTTP packet mime information, such as XML MIME types being recognized as XML. In 1.4, JSON generates a JavaScript object, and script executes it. The data returned by the server side is then parsed against this value and passed to the callback function. Available values:

"XML": Returns an XML document that can be processed with jQuery.

HTML: Returns plain text HTML information, and the included script tag executes when the DOM is inserted.

Script: Returns the plain text JavaScript code. Results are not automatically cached. Unless the "cache" parameter is set. Note: At remote request (not in the same domain), all

POST requests are converted to get requests. (because it will be loaded using the DOM's script tag)

"JSON": Returns JSON data.

"JSONP": Jsonp format. When calling a function using JSONP form, such as "myurl?callback=?" JQuery is automatically replaced? To 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). Call this function when a request fails.

There are three parameters: XMLHttpRequest object, error message, optionally caught exception object.

If an error occurs, the error message (the second argument) may be "timeout", "error", "Notmodified", and "ParserError" in addition to being null.

This is an Ajax event.

Global

Type: Boolean

Whether to trigger global AJAX events. Default value: True. Setting to FALSE will not trigger global AJAX events, such as Ajaxstart or ajaxstop, that can be used to control different AJAX events.

Ifmodified

Type: Boolean

Gets new data only when the server data changes. Default value: False. Use HTTP packet last-modified header information to determine. In JQuery 1.4, it also checks the server-specified ' ETag ' to determine that the data has not been modified.

Jsonp

Type: String

Overrides the name of the callback function in a JSONP request. This value is substituted for the "callback" section of the URL parameter in the GET or POST request in "callback=?", such as {jsonp: ' onjsonpload ' will cause "onjsonpload=?" to be passed to the server.

Jsonpcallback

Type: String

Specifies a callback function name for the JSONP request. This value will be used to replace the random function name that jQuery automatically generates. This is primarily used to allow jQuery to generate unique function names, which makes it easier to manage requests and easily provides callback functions and error handling. You can also specify this callback function name when you want the browser to cache a GET request.

Password

Type: String

The password used to respond to HTTP access authentication requests

ProcessData

Type: Boolean

Default value: True. By default, data that is passed in through the data option, if it is an object (technically, as long as it is not a string), is processed into a query string to match the default content type "application/x-www-form-urlencoded". Set to False if you want to send DOM tree information or other information that you do not want to convert.

Scriptcharset

Type: String

Only DataType is "JSONP" or "script" when requested, and type "get" is used to force modification of CharSet. Usually used only when the local and remote content encoding is different.

Success

Type: Function

The callback function after the request succeeds.

Parameters: Data returned by the server, processed according to the DataType parameter, and a string describing the state.

This is an Ajax event.

Traditional

Type: Boolean

If you want to serialize data in a traditional way, set it to true. Please refer to the Jquery.param method below for tool classification.

Timeout

Type: Number

Sets the request timeout (in milliseconds). This setting overrides the global setting.

Type

Type: String

Default value: "Get"). Request Mode ("POST" or "get"), default to "get". Note: Other HTTP request methods, such as put and DELETE, are also available, but only partially supported by browsers.

Url

Type: String

Default value: Current page address. The address where the request was sent.

Username

Type: String

The user name used to respond to HTTP access authentication requests.

Xhr

Type: Function

A XMLHttpRequest object needs to be returned. The default is ActiveXObject under IE, and in other cases it is xmlhttprequest. Used to override or provide an enhanced XMLHttpRequest object. This parameter is not available until JQuery 1.3.