function UrlExists(url) { var http = new XMLHttpRequest(); http.open('HEAD', url, false); http.send(); return http.status!=404; } code example

Example: javascript check if file exists on server

function doesFileExist(urlToFile) {
    var xhr = new XMLHttpRequest();
    xhr.open('HEAD', urlToFile, false);
    xhr.send();
     
    if (xhr.status == "404") {
        return false;
    } else {
        return true;
    }
}