正则表达式可验证空白字段，仅允许包含字符的空格

Question

I have a form that use a regular expression that validate characters only alongwith whitespace, but I have a problem, this doesn't validate empty fields. My expression regular is this :

regex = /^\s*[a-zA-Z ]{2,30}$/;

Answer 1

If you want to validate an empty field as well, you can provide an alternative for the whole pattern by putting |^$ onto the end, thus matching the empty string too (that is, match the position at the beginning of the string, immediately followed by the position at the end of the string):

 <form> <input pattern="^\\s*[a-zA-Z ]{2,30}$|^$"> <button>submit</button> </form>