platform/video.videojs/dist/video.es.js
function getFileExtension(path) {
  if (typeof path === 'string') {
    var splitPathRe = /^(\/?)([\s\S]*?)((?:\.{1,2}|[^\/]+?)(\.([^\.\/\?]+)))(?:[\/]*|[\?].*)$/i;
    var pathParts = splitPathRe.exec(path);

    if (pathParts) {
      return pathParts.pop().toLowerCase();
    }
  }

  return '';
}
function getFileExtension(path) {
  if (typeof path === 'string') {
    var splitPathRe = /^(\/?)([\s\S]*?)((?:\.{1,2}|[^\/]+?)(\.([^\.\/\?]+)))(?:[\/]*|[\?].*)$/i;
    var pathParts = splitPathRe.exec(path);

    if (pathParts) {
      return pathParts.pop().toLowerCase();
    }
  }

  return '';
}
Returns the extension of the passed file name. It will return an empty string
if passed an invalid path.

@param {string} path
The fileName path like '/path/to/file.mp4'

@returns {string}
The extension in lower case or an empty string if no
extension could be found.