Summarize the explanation of the meaning of each parameter in ajax

The content of this article is to summarize the explanation of the meaning of each parameter in ajax. It has certain reference value. Friends in need can refer to it. I hope it will be helpful to you.

1.url:
The requirement is a parameter of type String, (default is the current page address) The address to send the request.

2.type:
Requires parameters of type String, request method (post or get ) defaults to get. Note that other http request methods such as put and delete can also be used, but are only supported by some browsers.

3.timeout:
The requirement is a parameter of type Number, set the request timeout (milliseconds). This setting will override the global setting of the $.ajaxSetup() method.

4.async:
Requires parameters of type Boolean, the default setting is true, all requests are Asynchronous request. If you need to send synchronous requests, set this option to false. Note that a synchronous request will lock the browser , and the user must wait for the request to complete before other operations can be performed.

5.cache:
Requires parameters of type Boolean, the default is true (when dataType is script, the default is false), set to falsewill not load request information from the browser cache.

6.data:
Requires parameters of type Object or String, Data sent to the server. If it is not a string, will be automatically converted to string format . The get request will be appended with after the url. To prevent this automatic conversion, you can view the processData (prevent automatic conversion) option. The object must be in key/value format, for example {foo1:"bar1",foo2:"bar2"} is converted to &foo1=bar1&foo2=bar2. If it is an array, JQuery will automatically assign the same name to different values. For example, {foo:["bar1","bar2"]} is converted to &foo=bar1&foo=bar2.

7.dataType:
Requires parameters of type String, and expects the data type returned by the server. If does not specify , JQuery will automatically return responseXML or responseText based on the http package mime information and pass it as a callback function parameter. The available types are as follows:
XML: Returns an XML document that can be processed with JQuery.
　html: Returns plain text HTML information; the included script tag will be executed when inserted into the DOM.
　script: Returns plain text JavaScript code. Results are not automatically cached. Unless cache parameters are set. Note that when making remote requests (not under the same domain), all post requests will be converted into get requests.
json: Return JSON data.
jsonp: JSONP format. When calling a function using the SONP form, such as myurl?callback=?, JQuery will automatically replace the last "?" with the correct function name to execute the callback function.
Text: Returns a plain text string.

8.beforeSend：
This parameter is mainly used to perform some operations before sending a request to the server . The parameter is required to be a Function type. You can modify the function of the XMLHttpRequest object before sending the request, such as adding a custom HTTP header. If false is returned in beforeSend, this ajax request can be canceled. The XMLHttpRequest object is the only parameter.

        function(XMLHttpRequest){
               this;   //调用本次ajax请求时传递的options参数
            }

9.complete：
The requirement is a parameter of type Function, and the callback function called after the request is completed ( Called when the request succeeds or fails). Parameters: XMLHttpRequest object and a string describing the successful request type.

       function(XMLHttpRequest, textStatus){
             this;    //调用本次ajax请求时传递的options参数
          }

10.success：

The requirement is a parameter of type Function, called after the request is successful Callback function has two parameters.
        (1) Data returned by server and processed according to the dataType parameter.
(2) The string of the state .

         function(data, textStatus){
            //data可能是xmlDoc、jsonObj、html、text等等
            this;  //调用本次ajax请求时传递的options参数
         }

11.error:
is required to be a parameter of Function type, which is the function to be called when the request fails. This function has three parameters, namely XMLHttpRequest object, error message, and captured error object (optional). The ajax event function is as follows:

       function(XMLHttpRequest, textStatus, errorThrown){
          //通常情况下textStatus和errorThrown只有其中一个包含信息
          this;   //调用本次ajax请求时传递的options参数
       }

12.contentType:
requires parameters of String type. When sending information to the server, the content encoding type defaults to "application/ x-www-form-urlencoded". This default value is suitable for most applications.

13.dataFilter：
要求为Function类型的参数，给Ajax返回的原始数据进行预处理的函数。提供data和type两个参数。data是Ajax返回的原始数据，type是调用jQuery.ajax时提供的dataType参数。函数返回的值将由jQuery进一步处理。

           function(data, type){
                //返回处理后的数据
                return data;
            }

14.dataFilter：
要求为Function类型的参数，给Ajax返回的原始数据进行预处理的函数。提供data和type两个参数。data是Ajax返回的原始数据，type是调用jQuery.ajax时提供的dataType参数。函数返回的值将由jQuery进一步处理。

            function(data, type){
                //返回处理后的数据
                return data;
            }

15.global：
要求为Boolean类型的参数，默认为true。表示是否触发全局ajax事件。设置为false将不会触发全局ajax事件，ajaxStart或ajaxStop可用于控制各种ajax事件。

16.ifModified：
要求为Boolean类型的参数，默认为false。仅在服务器数据改变时获取新数据。服务器数据改变判断的依据是Last-Modified头信息。默认值是false，即忽略头信息。

17.jsonp：
要求为String类型的参数，在一个jsonp请求中重写回调函数的名字。该值用来替代在"callback=?"这种GET或POST请求中URL参数里的"callback"部分，例如{jsonp:'onJsonPLoad'}会导致将"onJsonPLoad=?"传给服务器。

18.username：
要求为String类型的参数，用于响应HTTP访问认证请求的用户名。

19.password：
要求为String类型的参数，用于响应HTTP访问认证请求的密码。

20.processData：
要求为Boolean类型的参数，默认为true。默认情况下，发送的数据将被转换为对象（从技术角度来讲并非字符串）以配合默认内容类型"application/x-www-form-urlencoded"。如果要发送DOM树信息或者其他不希望转换的信息，请设置为false。

21.scriptCharset：
要求为String类型的参数，只有当请求时dataType为"jsonp"或者"script"，并且type是GET时才会用于强制修改字符集(charset)。通常在本地和远程的内容编码不同时使用。

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