Clean JS code

JS files (pages, components, classes ...) in the src folde rare polluted by wrong practices. They need to be cleaned up.

To-do's:

• Correct errors and warnings in console
• Remove blank lines
• Remove useless comments
• Remove useless imports
• Remove useless console.log
• Remove useless variables (creating a variable before returning it)
• Convert wrong variables (var to const or let)
• Correct wrong imports (require instead of import from)
• Create global functions in Utils.js for re-used things (ex: url building from env variables like loginUrl)