[JavaScript] Correct handling for older browsers and missing casing

[AutomatedTester]

This brings back IE11 support and fixes the case where there is className

Fixes #17448 and #17447

🔗 Related Issues

💥 What does this PR do?

🔧 Implementation Notes

🤖 AI assistance

• No substantial AI assistance used
• AI assisted (complete below)
  • Tool(s):
  • What was generated:
  • I reviewed all AI output and can explain the change

💡 Additional Considerations

🔄 Types of changes

• Cleanup (formatting, renaming)
• Bug fix (backwards compatible)
• New feature (non-breaking change which adds functionality and tests!)
• Breaking change (fix or feature that would cause existing functionality to change)