Update

public/assets/js/mastodon.js

@@ -28,6 +28,26 @@ async function fetchData(log, tpl) {
             }
 
             if(key == "content") {
+                let text = value;
+
+                let youtube_frame_arr = [];
+                let spl_arr = text.split('"');
+                let youtube_link_start = 'https://www.youtube.com/watch?v=';
+
+                for (i = 0; i < spl_arr.length; i++) {
+                    if (spl_arr[i].indexOf(youtube_link_start) === 0) {
+                        let id = spl_arr[i].replace(youtube_link_start, '');
+                        let text_frame = `<iframe width="560" height="315" src="https://www.youtube.com/embed/${id}" title="YouTube video player" frameborder="0" allow="accelerometer; autoplay; clipboard-write; encrypted-media; gyroscope; picture-in-picture; web-share" allowfullscreen></iframe>`;
+                        youtube_frame_arr.push(text_frame);
+                    }
+                }
+
+                youtube_frame_arr.forEach(function(elem) {
+                    text += elem;
+                });
+
+                value = text;
+
                 post_tpl = post_tpl.replace('{content}', `${value}`);
             }