As of Drupal 8 all JS needs to follow our JavaScript coding standards. For this we use ESLint to check most of our standards.
Here is the summary of running ESLint on this module JS:
✖ 8 problems (8 errors, 0 warnings)
Attached is the full list of errors found by ESLint and the patch that fixes them. I think jquery.tablesorter.js file should be provided as a external library and not included in the module.