Refactor code structure for improved readability and maintainability

docs/assets/example/tool.thumbnail.js

@@ -0,0 +1,69 @@
+if (window.lastThumbnail) {
+    window.lastThumbnail.destroy();
+}
+
+var $popups = document.querySelector('.popups');
+var $popinner = document.querySelector('.popinner');
+var $artplayer = document.querySelector('.artplayer-app');
+
+$artplayer.innerHTML = 'Drop video file here or click to upload.';
+var thumbnail = new ArtplayerToolThumbnail({
+    fileInput: $artplayer,
+    number: 60, // 数量
+    width: 160, // 宽度
+    column: 10, // 列数
+    begin: 0, // 开始
+    end: NaN, // 结束
+});
+
+window.lastThumbnail = thumbnail;
+
+thumbnail.on('file', function (file) {
+    console.log('Read video successfully: ' + file.name);
+});
+
+thumbnail.on('video', function (video) {
+    console.log('Video size: ' + video.videoWidth + ' x ' + video.videoHeight);
+    console.log('Video duration: ' + video.duration + 's');
+    thumbnail.start();
+});
+
+thumbnail.on('canvas', function (canvas) {
+    console.log('Build canvas successfully');
+    console.log('Canvas size: ' + canvas.width + ' x ' + canvas.height);
+    console.log('Preview density: ' + thumbnail.density + ' p/s');
+});
+
+thumbnail.on('update', function (url, percentage) {
+    console.log('Processing: ' + Math.floor(percentage.toFixed(2) * 100) + '%');
+    $popups.style.display = 'flex';
+    $popinner.style.backgroundImage = 'url(' + url + ')';
+});
+
+thumbnail.on('download', function (name) {
+    console.log('Start download preview: ' + name);
+});
+
+thumbnail.on('done', function () {
+    $popups.style.display = 'none';
+    thumbnail.download();
+    console.log('Build preview image complete');
+
+    [...Artplayer.instances].forEach(function (art) {
+        art.destroy(true);
+    });
+
+    new Artplayer({
+        container: $artplayer,
+        url: thumbnail.videoUrl,
+        autoSize: true,
+        poster: thumbnail.thumbnailUrl,
+        thumbnails: {
+            url: thumbnail.thumbnailUrl,
+            number: thumbnail.option.number,
+            column: thumbnail.option.column,
+        },
+    });
+
+    console.log('Build player complete');
+});