JavaScript AJAX Check if a file exists via a HEAD request
Example
This function executes an AJAX request using the HEAD method allowing us to check whether a file exists in the directory given as an argument. It also enables us to launch a callback for each case (success, failure).
function fileExists(dir, successCallback, errorCallback) {
var xhttp = new XMLHttpRequest;
/* Check the status code of the request */
xhttp.onreadystatechange = function() {
return (xhttp.status !== 404) ? successCallback : errorCallback;
};
/* Open and send the request */
xhttp.open('head', dir, false);
xhttp.send();
};
