how to set input pattern for : if start with 4 then length is 16 digets if starts with 6 then length is 17 digets
for example:
when input starts with 6 then it must be: pattern="\d{4} \d{4} \d{4} \d{4} \d{1}"
But when input starts with 4 it must be: pattern="\d{4} \d{4} \d{4} \d{4}"
how to set pattern??