Detailed decryption Jsonp cross-domain request _javascript tips

1. What is cross-domain request:

A page on server A that requests a handler on Server B, which is called a cross-domain request

The test page for this time is:

Handler Kimhandler.ashx, as follows:

%@ WebHandler language= "C #" class= "Kimhandler"%>

using System;
Using System.Web;

public class Kimhandler:ihttphandler {public
  
  void ProcessRequest (HttpContext context)
  {
    string msg = ' {\ ' n Ame\ ": \ kim\", "gender\": \ "men \", "age\": ";
    Context. Response.Write (msg);
 
  public bool IsReusable {get
    {return
      false;
}}}

The other handler handler.ashx as follows:

<%@ WebHandler language= "C #" class= "Handler"%>

using System;
Using System.Web;

public class Handler:ihttphandler {public
  
  void ProcessRequest (HttpContext context)
  {
    string callbackname = Context. request.params["Callbackfun"];
    String msg = callbackname+ "({\" name\ ": \" kim\ ", \" age\ ": \" 18\ "});";
    Context. Response.Write (msg);
 
  public bool IsReusable {get
    {return
      false;

}}}

2.Ajax cannot implement Cross-domain request

<meta http-equiv= "Content-type" content= "text/html; Charset=utf-8 "/>
  <title></title>
  <script>
    var requesturl =" http:// Qxw1192430265.my3w.com/kimhandler.ashx ";
    Window.onload = function () {
      document.getElementById ("Btnajax"). onclick = function () {
        var xhr = new xmlhttprequ EST ();
        Xhr.open ("Get", Requesturl, true);
        Xhr.setrequestheader ("If-modified-since", 0);
        Xhr.onreadystatechange = function () {
          if (xhr.readystate = = 4 && xhr.status =) {
            var res = Xhr.res Ponsetext;
            Alert (res);
          }
        Xhr.send (null);
      }
  </script>
 
 

View monitor, found no return of any request report style

3. Using the script tag, you can implement cross domain requests

The test code is as follows:

<! DOCTYPE html>
 
 

View monitor, you can see, there are return request report style

Look in the JSON format

4. Use JS mode , in the browser side, read the response is the data

Test code as follows, note that a handler has been changed

<! DOCTYPE html>
 
 

Through the background code, we can know

And watch it on the monitor.

Found in the browser side, pop up Kim and 18

5. Use JQ to implement Cross-domain requests (the internal principle is to create a script tag for us)

The code is as follows

 <! DOCTYPE html>  
 

Click on the button, you can see the effect, and then look at the monitor

The above mentioned is the entire content of this article, I hope you can enjoy.