only use images that have a minimum size and delete outdated images

www/js/webcam.js

@@ -0,0 +1,35 @@
+const images = document.getElementsByClassName('current_webcam_image');
+const reload_interval = setInterval(reloadImages, 10000);
+
+window.onload = function() {
+    reloadImages();
+  };
+
+function checkImageSource(image_url) {
+    var http_request = new XMLHttpRequest();
+    http_request.open('HEAD', image_url, false);
+    http_request.send();
+
+    return http_request.status;
+}
+
+function reloadImages() {
+    console.log('reload in progress');
+
+    Array.prototype.forEach.call(images, function(image) {
+
+        if (checkImageSource(image.src) == 200) {
+            if (!image.src.includes('?')) {
+                image.src = `${image.src}?${Date.now()}`;
+            } else {
+                image.src = image.src.slice(0, image.src.indexOf('?') + 1) + Date.now();
+            }
+        } else {
+            console.log('unable to find image on server');
+            image.alt = "Webcam nicht erreichbar."
+
+            
+        }
+    });
+    console.log('reload finished');
+}