jQuery.ajax()

---

jQuery.ajax( url [, settings ] )Returns: jqXHR

Description: Perform an asynchronous HTTP (Ajax) request.

• version added: 1.5jQuery.ajax( url [, settings ] )

  • url
    Type: String
    A string containing the URL to which the request is sent.
  • settings
    Type: PlainObject
    A set of key/value pairs that configure the Ajax request. All settings are optional. A default can be set for any option with $.ajaxSetup(). See jQuery.ajax( settings ) below for a complete list of all settings.
  • //解释一下：URL为必要选项，settings是对ajax的一些配置，都是可选的。
    

• version added: 1.0jQuery.ajax( [settings ] )

  • settings
    Type: PlainObject
    A set of key/value pairs that configure the Ajax request. All settings are optional. A default can be set for any option with $.ajaxSetup().
  • //解释一下：所有设置均是以键&＃20540;对的形式进行设置的，而且都是可选的。
    
    • accepts (default: depends on DataType)
      Type: PlainObject
      The content type sent in the request header that tells the server what kind of response it will accept in return.
    • //解释一下：accepts在请求头里面设置响应的数据返回类型（默认是dataType里面设置的&＃20540;）。
      
    • async (default: true)
      Type: Boolean
      By default, all requests are sent asynchronously (i.e. this is set to true by default). If you need synchronous requests, set this option to false. Cross-domain requests and dataType: "jsonp" requests do not support synchronous operation. Note that synchronous requests may temporarily lock the browser, disabling any actions while the request is active. As of jQuery 1.8, the use of async: false with jqXHR ($.Deferred) is deprecated; you must use the success/error/complete callback options instead of the corresponding methods of the jqXHR object such as jqXHR.done() or the deprecated jqXHR.success().
    • //解释一下：async是指处理请求时是否是异步处理（布尔类型），设置TRUE表示异步处理（默认&＃20540;为TRUE）。当你需要同步请求时，设置为FALSE。跨域和dataType为jsonp的情况不支持同步这个选项。需要注意的是设置为同步可能会锁住浏览器，让其他请求不可用。所以一般设置为TRUE。
      
    • beforeSend
      Type: Function( jqXHR jqXHR, PlainObject settings )
      A pre-request callback function that can be used to modify the jqXHR (in jQuery 1.4.x, XMLHTTPRequest) object before it is sent. Use this to set custom headers, etc. The jqXHR and settings objects are passed as arguments. This is an Ajax Event. Returning false in the beforeSend function will cancel the request. As of jQuery 1.5, the beforeSend option will be called regardless of the type of request.
    • //解释一下：beforeSend设置发送请求前的动作。
      
    • cache (default: true, false for dataType 'script' and 'jsonp')
      Type: Boolean
      If set to false, it will force requested pages not to be cached by the browser. Note: Setting cache to false will only work correctly with HEAD and GET requests. It works by appending "_={timestamp}" to the GET parameters. The parameter is not needed for other types of requests, except in IE8 when a POST is made to a URL that has already been requested by a GET.
    • //解释一下：cache缓存，默认是TRUE（有缓存的）。如果设置为FALSE，则不会缓存。注意，只有在请求方式为head和get时，才能设置不缓存。
      
    • complete
      Type: Function( jqXHR jqXHR, String textStatus )
      A function to be called when the request finishes (after success and error callbacks are executed). The function gets passed two arguments: The jqXHR (in jQuery 1.4.x, XMLHTTPRequest) object and a string categorizing the status of the request ("success", "notmodified", "error", "timeout", "abort", or "parsererror"). As of jQuery 1.5, the complete setting can accept an array of functions. Each function will be called in turn. This is an Ajax Event.
    • //解释一下：complete请求完成时（无论成功与否）执行的回调函数，有两个参数jqXHR和textStatus。textStatus有以下几种状态：success（成功）、notmodified（没有修改）、error（错误）、timeout（请求超时）、abort（请求被废弃）、parseerror（请求时转换错误）。
      
    • contents
    • Type: PlainObject
      An object of string/regular-expression pairs that determine how jQuery will parse the response, given its content type. (version added: 1.5)
    • //解释一下：contents设置正则表达式来决定jQuery怎么来转换响应。
      
    • contentType (default: 'application/x-www-form-urlencoded; charset=UTF-8')
      Type: String
      When sending data to the server, use this content type. Default is "application/x-www-form-urlencoded; charset=UTF-8", which is fine for most cases. If you explicitly pass in a content-type to $.ajax(), then it is always sent to the server (even if no data is sent). The W3C XMLHttpRequest specification dictates that the charset is always UTF-8; specifying another charset will not force the browser to change the encoding. Note: For cross-domain requests, setting the content type to anything other than application/x-www-form-urlencoded, multipart/form-data, or text/plain will trigger the browser to send a preflight OPTIONS request to the server.
    • //解释一下：contentType编码设置，默认是 'application/x-www-form-urlencoded; charset=UTF-8'。utf-8编码，国际通用编码，默认就行了，适用绝大多数情况。
      
    • context
      Type: PlainObject
      This object will be made the context of all Ajax-related callbacks. By default, the context is an object that represents the ajax settings used in the call ($.ajaxSettings merged with the settings passed to $.ajax). For example, specifying a DOM element as the context will make that the context for the complete callback of a request, like so:

      1 2 3 4 5 6

      $.ajax({ url: "test.html", context: document.body }).done(function() { $( this ).addClass( "done" ); });

    • //解释一下：context上下文，通常可以定义一个变量来存放上下文。
      
    • converters (default: {"* text": window.String, "text html": true, "text json": jQuery.parseJSON, "text xml": jQuery.parseXML})
      Type: PlainObject
      An object containing dataType-to-dataType converters. Each converter's value is a function that returns the transformed value of the response. (version added: 1.5
    • //解释一下：converters转换器，默认&＃20540;是{"* text": window.String, "text html": true, "text json": jQuery.parseJSON, "text xml": jQuery.parseXML}。
      
    • crossDomain (default: false for same-domain requests, true for cross-domain requests)
      Type: Boolean
      If you wish to force a crossDomain request (such as JSONP) on the same domain, set the value of crossDomain to true. This allows, for example, server-side redirection to another domain. (version added: 1.5)
    • //解释一下：crossDomain跨域，默认&＃20540;是FALSE。
      
    • data
      Type: PlainObject or String or Array
      Data to be sent to the server. It is converted to a query string, if not already a string. It's appended to the url for GET-requests. See processData option to prevent this automatic processing. Object must be Key/Value pairs. If value is an Array, jQuery serializes multiple values with same key based on the value of the traditional setting (described below).
    • //解释一下：data以键&＃20540;对的形式向服务器发送数据，通常可以将表单里面的数据传递$("#form").serialize()。
      
    • dataFilter
      Type: Function( String data, String type )=>Anything
      A function to be used to handle the raw response data of XMLHttpRequest. This is a pre-filtering function to sanitize the response. You should return the sanitized data. The function accepts two arguments: The raw data returned from the server and the 'dataType' parameter.
    • //解释一下：dataFilter数据过滤器。
      
    • dataType (default: Intelligent Guess (xml, json, script, or html))
      Type: String
      The type of data that you're expecting back from the server. If none is specified, jQuery will try to infer it based on the MIME type of the response (an XML MIME type will yield XML, in 1.4 JSON will yield a Javascript object, in 1.4 script will execute the script, and anything else will be returned as a string). The available types (and the result passed as the first argument to your success callback) are:

      • "xml": Returns a XML document that can be processed via jQuery.
      • "html": Returns HTML as plain text; included script tags are evaluated when inserted in the DOM.
      • "script": Evaluates the response as Javascript and returns it as plain text. Disables caching by appending a query string parameter, "_=[TIMESTAMP]", to the URL unless the cache option is set to true. Note: This will turn POSTs into GETs for remote-domain requests.
      • "json": Evaluates the response as JSON and returns a Javascript object. The JSON data is parsed in a strict manner; any malformed JSON is rejected and a parse error is thrown. As of jQuery 1.9, an empty response is also rejected; the server should return a response of null or {} instead. (See json.org for more information on proper JSON formatting.)
      • "jsonp": Loads in a JSON block using JSONP. Adds an extra "?callback=?" to the end of your URL to specify the callback. Disables caching by appending a query string parameter, "_=[TIMESTAMP]", to the URL unless the cache option is set to true.
      • "text": A plain text string.
      • multiple, space-separated values: As of jQuery 1.5, jQuery can convert a dataType from what it received in the Content-Type header to what you require. For example, if you want a text response to be treated as XML, use "text xml" for the dataType. You can also make a JSONP request, have it received as text, and interpreted by jQuery as XML: "jsonp text xml." Similarly, a shorthand string such as "jsonp xml" will first attempt to convert from jsonp to xml, and, failing that, convert from jsonp to text, and then from text to xml.
      • //解释一下：dataType返回的数据类型，通常有XML、json、script、text和HTML等。如果不设置，jQuery会根据响应的MIME类型设置。用的最多的是json、XML和text。
        
    • error
      Type: Function( jqXHR jqXHR, String textStatus, String errorThrown )
      A function to be called if the request fails. The function receives three arguments: The jqXHR (in jQuery 1.4.x, XMLHttpRequest) object, a string describing the type of error that occurred and an optional exception object, if one occurred. Possible values for the second argument (besides null) are "timeout", "error", "abort", and "parsererror". When an HTTP error occurs, errorThrown receives the textual portion of the HTTP status, such as "Not Found" or "Internal Server Error." As of jQuery 1.5, the error setting can accept an array of functions. Each function will be called in turn. Note: This handler is not called for cross-domain script and cross-domain JSONP requests. This is an Ajax Event.
    • //解释一下：error请求失败时调用的函数，有三个参数 jqXHR、textStatus、errorThrown。textStatus可能的&＃20540;：timeout、error、abort和parseerror。
      
    • global (default: true)
      Type: Boolean
      Whether to trigger global Ajax event handlers for this request. The default is true. Set to false to prevent the global handlers like ajaxStart or ajaxStop from being triggered. This can be used to control various Ajax Events.
    • //解释一下：global请求时是否触发全局的ajax事件，默认是TRUE。
      
    • headers (default: {})
      Type: PlainObject
      An object of additional header key/value pairs to send along with requests using the XMLHttpRequest transport. The header X-Requested-With: XMLHttpRequest is always added, but its default XMLHttpRequest value can be changed here. Values in the headers setting can also be overwritten from within the beforeSend function. (version added: 1.5)
    • //解释一下：headers键&＃20540;对的形式。
      
    • ifModified (default: false)
      Type: Boolean
      Allow the request to be successful only if the response has changed since the last request. This is done by checking the Last-Modified header. Default value is false, ignoring the header. In jQuery 1.4 this technique also checks the 'etag' specified by the server to catch unmodified data.
    • //解释一下：ifModified默认是FALSE，忽略header。
      
    • isLocal (default: depends on current location protocol)
      Type: Boolean
      Allow the current environment to be recognized as "local," (e.g. the filesystem), even if jQuery does not recognize it as such by default. The following protocols are currently recognized as local: file, *-extension, and widget. If the isLocal setting needs modification, it is recommended to do so once in the $.ajaxSetup() method. (version added: 1.5.1)
    • //解释一下：isLocal默认依赖于当前的协议。
      
    • jsonp
      Type: String
      Override the callback function name in a JSONP request. This value will be used instead of 'callback' in the 'callback=?' part of the query string in the url. So {jsonp:'onJSONPLoad'} would result in 'OnJSONPLoad=?' passed to the server. As of jQuery 1.5, setting the jsonp option to false prevents jQuery from adding the "?callback" string to the URL or attempting to use "=?" for transformation. In this case, you should also explicitly set the jsonpCallback setting. For example, { jsonp: false, jsonpCallback: "callbackName" }
    • //解释一下：jsonp查询时设置URL用的，如果设置jsonp：‘onJsonpLoad’就会向服务器传送OnJSONPLoad=?。在jQuery1.5后，设置{ jsonp: false, jsonpCallback: "callbackName" }。
      
    • jsonpCallback
      Type: String or Function()
      Specify the callback function name for a JSONP request. This value will be used instead of the random name automatically generated by jQuery. It is preferable to let jQuery generate a unique name as it'll make it easier to manage the requests and provide callbacks and error handling. You may want to specify the callback when you want to enable better browser caching of GET requests. As of jQuery 1.5, you can also use a function for this setting, in which case the value of jsonpCallback is set to the return value of that function.
    • //解释一下：jsonpCallback，JOSNP请求的回调函数。
      
    • mimeType
      Type: String
      A mime type to override the XHR mime type. (version added: 1.5.1)
    • //解释一下：mimeType设置MIME类型。
      
    • password
      Type: String
      A password to be used with XMLHttpRequest in response to an HTTP access authentication request.
    • //解释一下：password在XMLHttpRequest响应时加密的密码。
      
    • processData (default: true)
      Type: Boolean
      By default, data passed in to the data option as an object (technically, anything other than a string) will be processed and transformed into a query string, fitting to the default content-type "application/x-www-form-urlencoded". If you want to send a DOMDocument, or other non-processed data, set this option to false.
    • //解释一下：processData默认TRUE，针对contentType为 "application/x-www-form-urlencoded"。
      
    • scriptCharset
      Type: String
      Only applies when the "script" transport is used (e.g., cross-domain requests with "jsonp" or "script" dataType and "GET" type). Sets the charset attribute on the script tag used in the request. Used when the character set on the local page is not the same as the one on the remote script.
    • //解释一下：scriptCharset脚本编码。
      
    • statusCode (default: {})
      Type: PlainObject

      An object of numeric HTTP codes and functions to be called when the response has the corresponding code. For example, the following will alert when the response status is a 404:

      1 2 3 4 5 6 7

      $.ajax({ statusCode: { 404: function() { alert( "page not found" ); } } });

      If the request is successful, the status code functions take the same parameters as the success callback; if it results in an error (including 3xx redirect), they take the same parameters as the error callback.

      (version added: 1.5)
    • //解释一下：statusCode状态码，常见的有404、500等，具体参考百度。
      
    • success
      Type: Function( Anything data, String textStatus, jqXHR jqXHR )
      A function to be called if the request succeeds. The function gets passed three arguments: The data returned from the server, formatted according to the dataType parameter or the dataFilter callback function, if specified; a string describing the status; and the jqXHR (in jQuery 1.4.x, XMLHttpRequest) object. As of jQuery 1.5, the success setting can accept an array of functions. Each function will be called in turn. This is an Ajax Event.
    • //解释一下：success请求成功时被调用的函数，有三个参数data、textStatus和jqXHR。
      
    • timeout
      Type: Number
      Set a timeout (in milliseconds) for the request. This will override any global timeout set with $.ajaxSetup(). The timeout period starts at the point the $.ajax call is made; if several other requests are in progress and the browser has no connections available, it is possible for a request to time out before it can be sent. In jQuery 1.4.x and below, the XMLHttpRequest object will be in an invalid state if the request times out; accessing any object members may throw an exception. In Firefox 3.0&＃43; only, script and JSONP requests cannot be cancelled by a timeout; the script will run even if it arrives after the timeout period.
    • //解释一下：timeout设置请求的超时时间。
      
    • traditional
      Type: Boolean
      Set this to true if you wish to use the traditional style of param serialization.
    • //解释一下：traditional，设置TRUE使用传统的参数序列化。
      
    • type (default: 'GET')
      Type: String
      The type of request to make ("POST" or "GET"), default is "GET". Note: Other HTTP request methods, such as PUT and DELETE, can also be used here, but they are not supported by all browsers.
    • //解释一下：type请求的方式通常有post和get，默认为get。put和delete部分浏览器支持。
      
    • url (default: The current page)
      Type: String
      A string containing the URL to which the request is sent.
    • //解释一下：URL请求处理路径。
      
    • username
      Type: String
      A username to be used with XMLHttpRequest in response to an HTTP access authentication request.
    • //解释一下：username，HTTP认证时的用户名。
      
    • xhr (default: ActiveXObject when available (IE), the XMLHttpRequest otherwise)
      Type: Function()
      Callback for creating the XMLHttpRequest object. Defaults to the ActiveXObject when available (IE), the XMLHttpRequest otherwise. Override to provide your own implementation for XMLHttpRequest or enhancements to the factory.
    • //解释一下：xhr默认ActiveXObject（IE浏览器） or XMLHttpRequest（其余浏览器）。
      
    • xhrFields
      Type: PlainObject

      An object of fieldName-fieldValue pairs to set on the native XHR object. For example, you can use it to set withCredentials to true for cross-domain requests if needed.

      1 2 3 4 5 6

      $.ajax({ url: a_cross_domain_url, xhrFields: { withCredentials: true } });

      In jQuery 1.5, the withCredentials property was not propagated to the native XHR and thus CORS requests requiring it would ignore this flag. For this reason, we recommend using jQuery 1.5.1&＃43; should you require the use of it.

      (version added: 1.5.1)

$.ajax();

$.ajax({
  url: "http://fiddle.jshell.net/favicon.png",
  beforeSend: function( xhr ) {
    xhr.overrideMimeType( "text/plain; charset=x-user-defined" );
  }
})
  .done(function( data ) {
    if ( console && console.log ) {
      console.log( "Sample of data:", data.slice( 0, 100 ) );
    }
  });

// Assign handlers immediately after making the request,
// and remember the jqXHR object for this request
var jqxhr = $.ajax( "example.php" )
  .done(function() {
    alert( "success" );
  })
  .fail(function() {
    alert( "error" );
  })
  .always(function() {
    alert( "complete" );
  });
 
// Perform other work here ...
 
// Set another completion function for the request above
jqxhr.always(function() {
  alert( "second complete" );
});