字母和数字的组合匹配正则表达式

Question

I have a challenge with regular expression match that might be just too easy for one of you. I hope you can help me with this problem. I need to test a string format in one shot using javascript or VB.net.

The string could have two parts separated by one tilde char ~ such as str1~str2 or just one part without the tilde character such as str1 or str2.

Str1 is a sequence of 0 to 8 digits. When str1 has length zero, the tilde character does not exist either.

Str2 has a length of 0 to 25 characters and its format must be a combination of letters and digits. Please note that just letters or just digits are not good but any combination of both. When str2 has length zero, the tilde character does not exists.

Since the combination of str1~str2 is an optional field, both str1 and str2 may have length zero which results in empty value for str1~str2.

For example 12345678~ab2345cdef, and 12345 and ab2345 have all correct format but 12345678~abcdefgh and 12345678~70934527654 do not have correct format because the second part is not a combination of letters and digits.

I tried solutions with patters such as /^([\\d]{4,8})(~)([az\\d]{0,25})$/.test('12345678~ab2345cdef') which does not produce the right result although I get correct result for examples such as 123456 or ab1234.

Any idea please?

Thank you in advance

Answer 1

There are official documents, for example Regular Expressions and tutorials on Mastering Lookahead and Lookbehind .
As to your example, try following:

var re = /^(\d{4,8})*~?((?=\d*[a-z])(?=[a-z]*\d)[a-z\d]{0,25})*$/;  

//testing
re.test('12a345~jh44kjh'); //false. non-digit in 1st part
re.test('12345~jhkjh'); //false. no digits in 2nd part
re.test('12345~123:456'); //false. ":" is not allowed in 2nd part
re.test('12345~123456'); //false. no letters in 2nd part
re.test('12345~abc123456'); //true. 
re.test('12345~123456abc'); //true. 
re.test('12345~123abc456'); //true. 
re.test('12345~abc123def'); //true. 
re.test('12345'); //true. 2nd part is optional  
re.test('abc12345'); //true. 1st part is optional

Some explanations:
^ start of string
$ end of string
(something) capturing pattern
(?=something) non-capturing lookahead pattern
\\d{4,8} 4 to 8 digits
(?=\\d*[az]) zero or more digits and a letter ahead
(?=[az]*\\d) zero or more letters and a digit ahead
[az\\d]{0,25} allowed symbol set: lowercase letters and digits

Answer 2

Here's a solution in VB.NET. The pattern is in 3 parts rolled into one:

Pattern for the first part ie 1-8 digits

^[0-9]{1,8}$

Pattern for the second part ie 1-25 alphanumeric with at least 1 letter or number:

^(?=.*[A-Za-z])(?=.*\d)[A-Za-z\d]{1,25}$

Combination of the two, with the tilde:

^[0-9]{1,8}~(?=.*[A-Za-z])(?=.*\d)[A-Za-z\d]{1,25}$

The three patterns are joined together with | to form the single regular expression.

I've included a few test cases in the code.

Imports System.Text.RegularExpressions

Module Module1

    Sub Main()

        Dim Pattern As String
        Dim Parser As Regex
        Dim Tests As New List(Of String)

        Pattern = "^[0-9]{1,8}$|^(?=.*[A-Za-z])(?=.*\d)[A-Za-z\d]{1,25}$|^[0-9]{1,8}~(?=.*[A-Za-z])(?=.*\d)[A-Za-z\d]{1,25}$"
        Parser = New Regex(Pattern)

        Tests.Add("12345678~ab2345cdef")
        Tests.Add("12345")
        Tests.Add("ab2345")
        Tests.Add("12345678~abcdefgh")
        Tests.Add("12345678~70934527654")
        Tests.Add("12a345~jh44kjh")
        Tests.Add("123456789")
        Tests.Add("ABab73895zzz")
        Tests.Add("aaaaaBBBBBCCCCCdddddZZZZZ1")
        Tests.Add("aa0aaBB1BBCC2CCdd3ddZZ4ZZ")
        Tests.Add("0~aa0aaBB1BBCC2CCdd3ddZZ4ZZ")
        Tests.Add("12345~123___aaa")
        Tests.Add("a123~z9")
        Tests.Add("1~2a")
        Tests.Add("")

        For Each Input As String In Tests
            Console.WriteLine(String.Format("{0} {1}", Input, Parser.IsMatch(Input)))
        Next

        Console.ReadKey()

    End Sub

End Module

Answer 3

this is my solution:

/^(\d{1,8}|(?=\d*[a-z])(?=[a-z]*\d)[a-z\d]{2,25}|\d{1,8}~(?=\d*[a-z])(?=[a-z]*\d)[a-z\d]{2,25})$/

\\d{1,8} from 1 to 8 numbers

(?=\\d*[az])(?=[az]*\\d)[az\\d]{2,25} from 2 to 25 letters

\\d{1,8}~(?=\\d*[az])(?=[az]*\\d)[az\\d]{2,25} join of above cases by ~

test: https://jsfiddle.net/s2g0b6v9/2/