What is it that should be corrected? I see this in the description:

Examples
tailAndHead([1,2,3,4,5]) should return 945
tailAndHead([111,2345,66,78,900]) should return 7293
tailAndHead([35456,782,569,2454,875]) should return 12012

I see this is the right test:

tailAndHead([1,2,3,4,5]) should return 945

Perhaps you forgot to correct the description? )

Just a little bit more difficult. If I ask the user to return a number of calculation results, there is no additional conditions, the difficulty is a bit too low.

In fact, I designed a more complex test before this, there are many restrictions on the conditions, and ultimately because it is too complex, I chose to give it up ;-)

oops~My fault. just fixed. thanks for your feedback!

Seems like the harder part to this is finding where the decimal is in the number than using "Math---round() ceil() and floor()"

Just missing some info in the Details for the second two examples

tailAndHead([1,2,3,4,5]) should return 945
tailAndHead([111,2345,66,78,900]) should return WHAT?
tailAndHead([35456,782,569,2454,875]) should return WHAT?