src/import.js
function _getExtensionRegEx(ext=settings.get('extensions')) {
  let _ext = '(?:' + makeArray(ext).join('|') + ')';
  return new RegExp(_ext + '$');
}
function _getExtensionRegEx(ext=settings.get('extensions')) {
  let _ext = '(?:' + makeArray(ext).join('|') + ')';
  return new RegExp(_ext + '$');
}
function _getExtensionRegEx ( ext = settings . get ( 'extensions' ) ) { let _ext = '(?:' + makeArray ( ext ) . join ( '|' ) + ')' ; return new RegExp ( _ext + '$' ) ; }
Get a regular expression for the given selection of file extensions, which
will then be able to match file paths, which have those extensions.

@private
@param {Array|string} [ext=config.get('extensions')]     The extension(s).
@returns {RegExp}                                        File path matcher.
Get a regular expression for the given selection of file extensions which will then be able to match file paths which have those extensions .