If I have a URL to a video file, how can I detect if the resource pointed by the URL is valid and exists before it can be displayed? I've seen some answers suggesting AJAX, but I only know AJAX to send and retrieve some data, not to get the status of the file whether it exists or not.
For example, if I have a URL like http://www.example.com/video.mp4
, how could I check whether video.mp4
exists or not and can or cannot be retrieved?
You don't really need ajax, just create a video element, and see if it can load the source
var video = document.createElement('video');
video.onload = function() {
alert('success, it exsist');
// show video element
}
video.onerror = function() {
alert('error, couldn\'t load');
// don't show video element
}
video.src = 'http://www.example.com/video.mp4';
Different browsers play different formats, to check if the file can be played in the current browser, you can use the canplaythrough
event
video.oncanplaythrough = function() {
alert("This file can be played in the current browser");
};
if the file is on the same domain, and ports and protocol match, you can use ajax to do a HEAD request and see if the resource exists, but that won't work cross-domain
var http = new XMLHttpRequest();
http.open('HEAD', '/folder/video.mp4');
http.onreadystatechange = function() {
if (this.readyState == this.DONE) {
if (this.status != 404) {
// resource exists
}
}
};
http.send();
You can send a HEAD
request. HEAD
requests send back only the HTTP headers, so if you get a status of 200 or 304 it means the resource exists, if you get a 404 it means the resource doesn't exist.
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