使用jQuery一次性获取YouTube或Vimeo缩略图

function getThumbnail(videoUrl, callback) {
  var videoId = getVideoId(videoUrl);
  if (videoId) {
    if (isYouTube(videoUrl)) {
      $.ajax({
        url: 'https://www.googleapis.com/youtube/v3/videos?id=' + videoId + '&key=YOUR_API_KEY&part=snippet',
        dataType: 'jsonp',
        success: function(data) {
          if (data.items && data.items.length > 0) {
            var thumbnailUrl = data.items[0].snippet.thumbnails.default.url;
            callback(thumbnailUrl);
          }
        }
      });
    } else if (isVimeo(videoUrl)) {
      $.ajax({
        url: 'https://vimeo.com/api/v2/video/' + videoId + '.json',
        dataType: 'json',
        success: function(data) {
          if (data && data.length > 0) {
            var thumbnailUrl = data[0].thumbnail_small;
            callback(thumbnailUrl);
          }
        }
      });
    }
  }
}

function getVideoId(videoUrl) {
  var videoId = null;
  if (isYouTube(videoUrl)) {
    videoId = videoUrl.match(/(?:https?:\/{2})?(?:w{3}\.)?youtu(?:be)?\.(?:com|be)(?:\/watch\?v=|\/)([^\s&]+)/)[1];
  } else if (isVimeo(videoUrl)) {
    videoId = videoUrl.match(/https?:\/\/(?:www\.)?vimeo.com\/(?:channels\/(?:\w+\/)?|groups\/([^\/]*)\/videos\/|album\/(\d+)\/video\/|video\/)?(\d+)(?:$|\/|\?)/)[3];
  }
  return videoId;
}

function isYouTube(videoUrl) {
  return videoUrl.indexOf('youtube.com') > -1 || videoUrl.indexOf('youtu.be') > -1;
}

function isVimeo(videoUrl) {
  return videoUrl.indexOf('vimeo.com') > -1;
}

getThumbnail('https://www.youtube.com/watch?v=VIDEO_ID', function(thumbnailUrl) {
  console.log(thumbnailUrl);
});

getThumbnail('https://vimeo.com/VIDEO_ID', function(thumbnailUrl) {
  console.log(thumbnailUrl);
});