Check url content type with javascript

Question

In order to conserve server resources I'm looking for a way to retrieve the content type of a given url using javascript. It should not download the complete content from the url only the headers. Is this possible with the restrictions javascript has.

Answer 1

Make an Ajax call with a head request.

var url = window.location.href;
var xhttp = new XMLHttpRequest();
xhttp.open('HEAD', url);
xhttp.onreadystatechange = function () {
    if (this.readyState == this.DONE) {
        console.log(this.status);
        console.log(this.getResponseHeader("Content-Type"));
    }
};
xhttp.send();

Answer 2

FYI if your server doesn't allow HEAD requests but does allow GET requests, you can do this by limiting the range of the GET request.

var xmlhttp = new XMLHttpRequest();
xmlhttp.open("GET", url, true);
xmlhttp.setRequestHeader("Range", "bytes=0");
xmlhttp.onreadystatechange = function () {
  if (this.readyState == this.DONE) {
    console.log(this.getResponseHeader("Content-Type"));
  }
};
xmlhttp.send();