A number is considered slidey if for every digit in the number, the next digit from that has an absolute difference of one. Check the examples below.
isSlidey(123454321) ➞ true
isSlidey(54345) ➞ true
isSlidey(987654321) ➞ true
isSlidey(1123) ➞ false
isSlidey(1357) ➞ false