Detailed explanation of how to implement Javascript cross-domain request code

Under what circumstances will cross-domain occur?

Assume that the domain name is: http://www.php.cn
If the requested domain name is different from this domain name, this situation is cross-domain. Since there are loopholes in cross-domain, it is generally For example, normal cross-domain request methods cannot be requested.
Solution:
1. window.name
1. The server returns

<script>window.name=&#39;{"id":"3", "name":"leisure"}&#39;;</script>

2. Define an iframe and add the onload event< ;iframe id="iframe1" onload="iLoad">d5ba1642137c3f32f4f4493ae923989c

<script type="text/javascript"> 
var load = false; 
function iLoad() { 
if(load == false) { 
// 同域处理，请求后会再次重新加载iframe 
document.getElementById(&#39;iframe1&#39;).contentWindow.location = &#39;/&#39;; 
load = true; 
} else { 
// 获取window.name的内容，注意必须进行同域处理后方可访问！ 
var data = document.getElementById(&#39;iframe1&#39;).contentWindow.name; 
alert(data); // {"id":"3", "name":"leisure"} 
load = false; 
} 
} 
</script>

3. Define a form, set the form's target to the iframe's id, and then submit the form

<form action="url" method="POST" target="iframe1"> 
<button type="submit" value="submit" /> 
</form>

2. JSONP
The server returns callback({"id": "3", "name": "leisure" });

<script type="text/javascript"> 
function callback(data) { 
alert(data); 
} 
</script> 
<script type="text/javascript" src="http://www.php.cn/product.jsp?id=5&jsonp=callback"></script>

3. jQuery.getJSON
The server returns json format data test({"id": "3", "name": "leisure" }); The test function name is defined in the callback parameter

$.getJSON(url + "?callback=?", data, function(data) { 
}

Note that the callback=? parameter must be brought, jquery will automatically generate a function name to replace the question mark! jQuery.getJSON is actually implemented using JSONP.

4. Flash cross-domain
Add crossdomain.xml to the server
http://www.php.cn/ crossdomain.xml

<?xml version="1.0"?> 
<cross-domain-policy> 
<allow-access-from domain="*.another.com.cn" /> 
</cross-domain-policy>

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