The Cross-domain problem of Native js implementing ajax

< script >

function loadXMLDoc()
{
    var xmlhttp;
    if (window.XMLHttpRequest)
    {
        //  IE7+, Firefox, Chrome, Opera, Safari 
        xmlhttp=new XMLHttpRequest();
    }
    else
    {
        // IE6, IE5 
        xmlhttp=new ActiveXObject("Microsoft.XMLHTTP");
    }
    xmlhttp.onreadystatechange=function()
    {
        if (xmlhttp.readyState==4 && (xmlhttp.status>=200&&xmlhttp.status<=300))
        {
            document.getElementById("myDiv").innerHTML=xmlhttp.responseText;
        }else{
            alert(xmlhttp.status);
        }
    }
        xmlhttp.open("GET","https://api.shenjian.io/promovie/piaofang?appid=fed023bfdffa5202e08665601d127045/",true);
        xmlhttp.send(null);
}

< / script >

write this for the first time, ask the boss to see what the problem is?
ajax, encapsulated with jQ can successfully obtain data by changing datatype from JOSN to JSONP, but if you want to implement it with a native method, it"s still a big problem

< script >

var url="https://api.shenjian.io/promovie/piaofang?appid=fed023bfdffa5202e08665601d127045";
          
           //xhr
           function createCORSXhr(url,method){
                var xhr=new XMLHttpRequest();
                if("withCredentials" in xhr){
                          xhr.open(method,url,true);                         
                    }else if(typeof XDomainRequest !=="undefined"){
                          xhr=new XDomainRequest();                            
                          xhr.open(method,url);    
                     }else
                          xhr=null;
                     return xhr;                     
                }
           
           //ajax
           function sendAjaxRequest(){
                var xhr=createCORSXhr(url,"get");
                //xhr.setRequestHeader("Origin","https://api.shenjian.io/promovie/piaofang?appid=fed023bfdffa5202e08665601d127045")   
                xhr.onload=function(){
                     if(xhr.readyState==4){
                     if(xhr.status>=200 && xhr.status<300 || xhr.status==304)
                          alert(xhr.responseText);
                          }else{
                               alert(" ajax error...")
                               }
                     }
                };
                xhr.onerror=function(){
                     alert("error code:"+xhr.status)
                }
                xhr.send(null);
                };

           sendAjaxRequest()

< / script >
someone wrote this on the Internet. He said that he could support cross-domain, but I tried to report the same mistake