Question

Is it possible to do a HTTP Head request solely using an XMLHTTPRequest in JavaScript?

My motivation is to conserve bandwidth.

If not, is it possible to fake it?

Answer 1

Easy, just use the HEAD method, instead of GET or POST:

function UrlExists(url, callback) {     var http = new XMLHttpRequest();     http.open('HEAD', url);     http.onreadystatechange = function() {         if (this.readyState == this.DONE) {             callback(this.status != 404);         }     };     http.send(); } 

This is just a short example to show how to use the HEAD method. Production code may need more fine-grained callbacks for different result states (success, failure, timeout), and may use different event handlers (onload, onerror and ontimeout rather than onreadystatechange).