.match(/[A-Z][a-z]+|[0-9]+/g).join(" ")
This should handle the numbers as well.. the join at the end results in concatenating all the array items to a sentence if that's what you looking for
'ThisIsTheStringToSplit'.match(/[A-Z][a-z]+|[0-9]+/g).join(" ")
Output
"This Is The String To Split"