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How jquery uses jsonp to obtain JSON data across domains (to solve jquery's cross-server permission restriction problem)

Source: Internet
Author: User
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HTML code:

<HTML xmlns = "http://www.w3.org/1999/xhtml">

 

<Head runat = "server">
<Title> </title>
<SCRIPT src = "jquery-1.3.2-vsdoc2.js" type = "text/JavaScript"> </SCRIPT>
<SCRIPT type = "text/JavaScript">
Function getdata (){
$. Ajax ({
URL: "http: // 192.168.2.32/jquery/ajax_do.aspx? Callback =? ",
Datatype: "jsonp ",
Jsonp: "Callback ",
Success: function (data ){
Alert (data );
$ ("# Sp_data" ).html (data. msg );
}
});
}
</SCRIPT>
</Head>
<Body>
<Div>
<A onclick = "getdata ()" href = "#" style = "color: Blue"> Cross-origin </a>
</Div>
</Body>
</Html>

 

 

Background code (ajax_do.aspx.cs ):

 

String callback = request. querystring ["Callback"];
Response. Write (callback + "({MSG: 'error action! '})");

 

 

Jsonp principle:

Register a callback on the client, and then pass the callback name to the server.

In this case, the server is converted into JSON data.

Then, a function is generated in Javascript syntax. The function name is the passed parameter jsonp.

Finally, place the JSON data directly in the function as an input parameter. In this way, a JS syntax document is generated and returned to the client.

The client browser parses the script tag and executes the returned JavaScript document. As a parameter, the data is passed into the pre-defined callback function of the client. (The callback function is dynamically executed)

 

 

 

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Related Keywords:
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