js implements object-oriented encapsulation of ajax requests_javascript skills

AJAX is a technology for creating fast, dynamic web pages. AJAX enables web pages to update asynchronously by exchanging small amounts of data with the server in the background. This means that parts of a web page can be updated without reloading the entire page.
Using ajax requests in js generally involves three steps:

• 1. Create XMLHttp object
  
• 2. Send a request: including opening a link and sending a request
  
• 3. Process the response
  

If you want to use ajax without using any js framework, you may need to write the code as below

<span style="font-size:14px;">var xmlHttp = xmlHttpCreate();//创建对象 
xmlHttp.onreadystatechange = function(){//响应处理 
  if(xmlHttp.readyState == 4){ 
    console.info("response finish"); 
    if(xmlHttp.status == 200){ 
       console.info("reponse success"); 
      console.info(xmlHttp.responseText); 
    } 
  } 
} 
xmlHttp.open("get","TestServlet",true);//打开链接 
 
xmlHttp.send(null);//发送请求 
 
function xmlHttpCreate() { 
  var xmlHttp; 
  try { 
    xmlHttp = new XMLHttpRequest;// ff opera 
  } catch (e) { 
    try { 
      xmlHttp = new ActiveXObject("Msxml2.XMLHTTP");// ie 
    } catch (e) { 
      try { 
        xmlHttp = new ActiveXObject("Microsoft.XMLHTTP"); 
      } catch (e) { 
 
      } 
    } 
  } 
  return xmlHttp; 
} 
 
console.info(xmlHttpCreate());</span> 

If you use this kind of ajax request in more complex business logic, the code will be bloated and inconvenient to reuse. And you can see that a business logic operation may need to be processed after the server responds successfully. At this time, you have to The operation is written in the onreadystatechage method.
In order to facilitate code reuse we can do the following;

• 1. After the server responds successfully, the business logic to be processed is left to the developer himself
• 2. Object-oriented encapsulation of requests

After processing it should look like this:

<pre code_snippet_id="342814" snippet_file_name="blog_20140513_2_2489549" name="code" class="javascript">window.onload = function() { 
  document.getElementById("hit").onclick = function() { 
    console.info("开始请求"); 
    ajax.post({ 
        data : 'a=n', 
        url : 'TestServlet', 
        success : function(reponseText) { 
          console.info("success : "+reponseText); 
        }, 
        error : function(reponseText) { 
          console.info("error : "+reponseText); 
        } 
    }); 
  } 
} 
 
var ajax = { 
  xmlHttp : '', 
  url:'', 
  data:'', 
  xmlHttpCreate : function() { 
    var xmlHttp; 
    try { 
      xmlHttp = new XMLHttpRequest;// ff opera 
    } catch (e) { 
      try { 
        xmlHttp = new ActiveXObject("Msxml2.XMLHTTP");// ie 
      } catch (e) { 
        try { 
          xmlHttp = new ActiveXObject("Microsoft.XMLHTTP"); 
        } catch (e) { 
 
        } 
      } 
    } 
    return xmlHttp; 
  }, 
  post:function(jsonObj){ 
    ajax.data = jsonObj.data; 
    ajax.url = jsonObj.url; 
    //创建XMLHttp对象，打开链接、请求、响应 
    ajax.xmlHttp = ajax.xmlHttpCreate(); 
    ajax.xmlHttp.open("post",ajax.url,true); 
    ajax.xmlHttp.onreadystatechange = function(){ 
      if(ajax.xmlHttp.readyState == 4){ 
        if(ajax.xmlHttp.status == 200){ 
          jsonObj.success(ajax.xmlHttp.responseText); 
        }else{ 
          jsonObj.error(ajax.xmlHttp.responseText); 
        } 
      } 
    } 
    ajax.xmlHttp.send(ajax.data); 
  } 
};

The above code implements ajax operations similar to jquery. I hope it will be helpful to everyone's learning.