正则表达式将alpha字符与第一个字符匹配，其余为字母数字

Question

我试着写一个正则表达式来匹配以下内容：

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

我能不能匹配

a
k2jdj
hello
example72812

Answer 1

你可以尝试

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

Answer 2

此？

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