refactor: code cleanup

[erisu]

Platforms affected

Android

Motivation and Context

Cleanup Code

Description

• use lambda functions
• remove redundant casting and types
• doctype fix
• use switch case
• use .isEmpty() instead of .length()==0
• remove unused import

Testing

npm t

Checklist

• I've run the tests to see all new and existing tests pass
• I added automated test coverage as appropriate for this change
• Commit is prefixed with (platform) if this change only applies to one platform (e.g. (android))
• If this Pull Request resolves an issue, I linked to the issue in the text above (and used the correct keyword to close issues using keywords)
• I've updated the documentation if necessary

[erisu]

Last call for reviews.