A brief introduction to jsonp usage summary_jquery

Jsonp (JSON with Padding) is a "usage mode" of json, which allows web pages to obtain data from other domain names (websites), that is, read data across domains.

Why do we need a special technology (JSONP) to access data from different domains (websites)? This is because of the same-origin policy.

The same-origin policy is a well-known security policy proposed by Netscape. All browsers that support JavaScript now use this policy.

First of all: jsonp is a tool used by json to cross domains.

The principle is to bypass the same-origin policy through the cross-domain feature of the script tag.

Tested and experimented:

Sender:

$.ajax({
type : "post",
url : "ajax.php",
dataType : "jsonp",
jsonp: "callback",//传递给请求处理程序或页面的，用以获得jsonp回调函数名的参数名(默认为:callback)
jsonpCallback:"jsonpcallback",//自定义的jsonp回调函数名称，默认为jQuery自动生成的随机函数名
success : function(json){
alert('success');
},
error:function(){
alert('fail');
}
}); 

Server side (php):

<&#63;php
$data = "aaa";
$callback = $_GET['callback'];
echo $callback.'('.json_encode($data).')';
exit;
&#63;>