Also, the scripts executed in a website that's protected by the same-origin policy are under restrictions. So, a request generated by the script follows the same rules. If we want to execute a request using JavaScript to avoid the same-origin policy, you need to force the script to execute it in order to comply with the rule and execute the request in the script, for example:

function( 
const Http = new XMLHttpRequest(); 
const url='https://jsonplaceholder.typicode.com/posts'; 
Http.open("GET", url); 
Http.send(); 
Http.onreadystatechange=(e)=>{ 
console.log(Http.responseText) 
} 
); 
 
<script> 
function function(message) { alert(message); } 
</script> 
<script src="http://testsite.com/file.aspx"> 
</script> 

In the preceding example, we are including the request in a JavaScript function. When the JavaScript function is loaded by the website, the code is also included, and executed as part of the same domain.