正則表達式表達字母字符匹配的第一個字符，其餘字母

Question

我試着寫一個正則表達式匹配以下：

must start with a letter 
the rest must be alphanumeric 
at least one character in length 
max characters 12 

如果我能夠匹配

a 
k2jdj 
hello 
example72812 

Answer 1

你可以試試

[a-zA-Z][a-zA-Z0-9]{0,11} 

Answer 2

這個？

[a-zA-Z][a-zA-Z0-9]{0,11}