正则表达式，长度为25个字符，以字母开头

Question

My 5 are conditions

• Trying to write regex for accepting alphanumeric string.
• It cannot start with number.
• Cannot have _ hence not using \\w .
• Length should be exactly 25 characters.
• First 5 should be alphabets and next 20 should be numeric.

here is my regex

var str = "Aasdfds133147852369852147";
var Exp = /^([A-Za-z]+[0-9]){25}$/;  //This fails..ERROR
//var Exp = /^([A-Za-z0-9]){25}$/;  This pass ..SUCCESS, but fails my second condition
if(!str.match(Exp)){
alert("ERROR");
}
else {
alert("SUCCESS");
}

Help me tune my code..

Answer 1

Is this:

/^[a-zA-Z][a-zA-Z0-9]{24}$/

what you're looking for?

regexr link ( with multiline)

Explanation:

• [a-zA-Z] checks if the first char is alphabetical.
• [a-zA-Z0-9]{24} checks if the next 24 characters are alphanumeric.

Answer 2

You can use this regex:

var exp = /^[A-Za-z][A-Za-z0-9]{24}$/;

Breakup:

^                # string start
[A-Za-z]         # match an alphabetic char
[A-Za-z0-9]{24}  # match 24 of an alphabetic char or a digit
$                # string end

Answer 3

It cannot start with number.

^(?!\d)

Cannot have _ hence not using \\w.

^(?!\d)[a-zA-Z0-9]

Length should be exactly 25 characters.

^(?!\d)[a-zA-Z0-9]{25}$

Answer 4

我有一个非常简单的解决方法

 var exp = /^[A-Za-z]{5}[A-Za-z0-9]{20}$/;