How to use the parameters of the $.Ajax() method

This time I will show you how to use the parameters of the $.Ajax() method, and what are the precautions for using the $.Ajax() method. The following is a practical case, let's take a look.

Let me first introduce to you the concept of Ajax

ajax method

1.url

2.type

http request methods, such as put and delete, can also be used, but are only supported by some browsers.

3.timeout

4.async

5.cache

6.data

7.dataType

data type returned by the server. If not specified, jQuery will automatically return responseXML or responseText based on the mine information of the HTTP package and pass it as a callback function parameter. The available types are as follows:

8.beforeSend

requires parameters of 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

requires a parameter of Function type, a callback function called after the request is completed (called whether 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

Requires parameters of Function type. The callback function called after the request is successful has two parameters.

　 (1) Data returned by the server and processed according to the dataType parameter.

　(2) A string describing the status.

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

11.error

requires 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

requires parameters of Function type, a function that preprocesses the original data returned by Ajax. Provide two parameters: data and type. data is the original data 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.

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

14.global

Requires parameters of Boolean type, defaults to true. Indicates whether to trigger the global ajax event. Setting to false will not trigger global ajax events, ajaxStart and ajaxStop can be used to control various ajax events.

15.ifModified

Requires parameters of Boolean type, defaults to false. Only get new data when server data changes. The basis for determining server data changes is the Last-Modified header information. The default value is false, which means header information is ignored.

16.jsonp

requires parameters of String type and rewrites the name of the callback function in a jsonp request. This value is used to replace the "callback" part of the URL parameter in a GET or POST request such as "callback=?". For example, {jsonp:'onJsonPLoad'} will cause "onJsonPLoad=?" to be passed to the server.

17.username

is required to be a parameter of String type, used to respond to the user of the HTTP access authentication request.

18.password

is required to be a String type parameter, which is the password used to respond to the HTTP access authentication request.

19.processData

Requires a Boolean type parameter, and the default is true. By default, the data sent will be converted to objects (technically not strings) to match the default content type "application/x-www-form-urlencoded". If you want to send DOM tree information or other information that you do not want to convert, please set it to false.

20.scriptCharset

requires parameters of String type. Only when the request dataType is "jsonp" or "script", and type It will be used to force the character set (charset) to be modified only when it is GET. Usually used when the local and remote content encodings are different.

Case code:

$(function(){
 $('#send').click(function(){
  $.ajax({
  type: "GET",
  url: "test.json",
  data: {username:$("#username").val(), content:$("#content").val()},
  dataType: "json",
  success: function(data){
    $('#resText').empty(); //清空resText里面的所有内容
    var html = '';
    $.each(data, function(commentIndex, comment){
    html += '
' + comment['username']
      + ':
';
    });
    $('#resText').html(html);
   }
  });
 });
});

Knowledge link:

1. $.each() function: $.each( ) function is different from the each() method of jQuery object. It is a global function and does not operate jQuery object. This function receives two parameters, the first parameter is an array or object, and the second parameter is a callback function. The callback function has two parameters: the first parameter is the index of the array or the member of the object, and the second parameter is the corresponding variable or content.

　　$.each(data,function(commentIndex,comment){
  //doSomething;
 })

2、ajaxStart()与ajaxStop()：当Ajax请求开始时，会触发ajaxStart()方法的回调函数。当Ajax请求结束时，会触发ajaxStop()方法的回调函数。这些方法都是全局的方法，因此无论创建它们的代码位于何处，只要有Ajax请求发生时，就会触发它们。

有时候页面需要加载一些图片，可能速度回比较慢，如果在加载过程中，不给用户提供一些提示和反馈信息，很容易让用户误认为按钮单击无用，使用户对网站失去信息。

此时，我们就需要为网页添加一个提示信息，常用的提示信息是“加载中...”，代码如下：

加载中...

当Ajax请求开始时，将此元素显示，用来提示用户Ajax请求正在进行；当Ajax请求结束后，将此元素隐藏。代码如下：

$("#loading").ajaxStart(function(){
　　　　$(this).show();
　　}).ajaxStop(function(){
 $(this).hide();
 })

好了，下面再给大家分享一个案例代码：

$(function(){
 $('#send').click(function(){
  $.ajax({
  type: "GET",
  url: "test.json",
  data: {username:$("#username").val(), content:$("#content").val()},
  dataType: "json",
  success: function(data){
    $('#resText').empty(); //清空resText里面的所有内容
    var html = ''; 
    $.each(data, function(commentIndex, comment){
    html += '
' + comment['username']
      + ':
';
    });
    $('#resText').html(html);
   }
  });
 });
});

end，代码到此结束。

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