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Ajax is widely used in web systems, but cross-domain issues are often encountered in web systems. By default, browsers prohibit Ajax cross-domain access. The IE browser has particularly strict restrictions. For browsers such as Firefox, Google, and Safari, it is relatively simple to use Ajax in JQuery for cross-domain access. The article "Ajax Cross-Domain Cookie Settings" introduces Ajax and the server involved in this issue. I will not go into details here.

Below we will focus on how to allow Ajax cross-domain access in IE browser.

From the above article, we know that if we only allow the browser to access across domains, it is also very simple. No modification is required on the browser side, just the normal Ajax code, and all the work is set up on the server side.

Ajax Code

$.ajax({
       url: 'http://www.onmpw.com/ajax.php',
       type: 'get',
       dataType: 'json',
       success: function (res) {
           console.log(res);
       },
       error: function (err) {
          console.log(err);
       }
 }) 

PHP code

$origin = $_SERVER['HTTP_ORIGIN'];
header("Access-Control-Allow-Origin:" . $origin);

Of course, for IE browser, the server side is actually the same. The difference is the front-end part. It is not that IE browser does not support the cross-domain method above. IE10+ can support it very well. This is something we should be happy about. After all, IE has left us a way out. However, IE8 and IE9 are still alive on most users' computers. So we also need to consider those persistent users.

We ran the above code on IE9 with a fluke mentality. The hope that had just been ignited was extinguished in an instant. What should we do? So we modified the Ajax code

$.ajax({
     url: 'http://www.onmpw.com/ajax.php',
     type: 'get',
     crossDomain: true,
     dataType: 'json',
     success: function (res) {
        console.log(res);
     },
     error: function (err) {
        console.log(err);
     }
 })

This time it should be fine, so I continued running. But my hope was wiped out again. After a while of searching, I suddenly realized that IE9 does not support crossDomain.

What should I do? Should I just give up on those users who are obsessed with IE9-? No, I have to give those users a reason to stick with it!

Although JQuery cannot access cross-domain in IE9-, you can use XDomainRequest provided by IE to access it. Let's see how to use it:

var xdr = new XDomainRequest(); // Use Microsoft XDR
xdr.open('get', 'http://www.onmpw.com/ajax.php');
xdr.onload = function () {
   var dom  = new ActiveXObject('Microsoft.XMLDOM'),JSON = $.parseJSON(xdr.responseText);
   dom.async = false;
   if (JSON == null || typeof (JSON) == 'undefined') {
         JSON = $.parseJSON(data.firstChild.textContent);
   }
   console.log(JSON.RES); //JSON.RES是返回结果
};
xdr.onerror = function() {
   _result = false;
};
xdr.send();

The above Ajax can finally run cross-domain on IE9- browser without changing the server-side code.

In general, IE has relatively strict restrictions on cross-domain issues. It is more troublesome for us programmers, but these problems must be solved.