The issue here is that a new feature was added in v6 that does not include ie11 supported code. The culprit is the because the userOptions is being spread onto an object.
https://github.com/focus-trap/focus-trap/blob/master/index.js#L48

Introduced in #125

Does this code get transpiled or should the src be compliant? I'd be happy to make a fix to it, just want to verify what the intention is!

Error is Expected identifier, string or number
@ this line

Steps to Recreate

• Update to v6
• Run in ie11 and see js errors