I've tried to open a file in my txt file using some js code but it does'nt seem to work, it says that i can only use http and https for that. The tutorial im watching is maybe too old that's why in it everything's working correctly. please solve my problem. Here's my code:

var fetchBtn = window.document.getElementById("fetchBtn");
var backupBtn = window.document.getElementById("backupBtn");

fetchBtn.onclick = function () {
    var x = new XMLHttpRequest();
    
    var file = "only.txt";
    x.open("GET", file, true);
    
    x.onload = function () {
        window.console.log(this.responseText);
    }
    
    x.send();
}