CODEWITHSUNDEEP
javascriptregex
snowcoder
snowcoder

Reputation: 491

Domain name regular expression

I am trying to find if a string has valid domain names or not in JavaScript. As per requirement, these are my valid and invalid domain names.

Valid Domain:

Invalid Domain:

below code is working as expected for both valid as well as invalid domain except "*google.com". I am still getting valid expression as result for "*google.com"

How can I fix this RegEx?

var fqdn = "aws.logs.security.stark.tony.com";
if (fqdn.match("^(?!-)[A-Za-z0-9-*]+([\\-\\.]{1}[a-z0-9]+)*\\.[A-Za-z]{2,6}$")) {
    console.log("Matched");
}
else{
    console.log("Not Matched");
}

Upvotes: 0

Views: 2220

Answers (1)

41686d6564
41686d6564

Reputation: 19661

You may use the following pattern:

^(?:\*\.)?[a-z0-9]+(?:[\-.][a-z0-9]+)*\.[a-z]{2,6}$

Regex demo.

Breakdown:

  • ^ - Beginning of string.
  • (?:\*\.)? - Match an optional "*." literally.
  • [a-z0-9]+ - One or more alphanumeric characters.
  • (?:[\-.][a-z0-9]+)* - A hyphen or a dot followed by one or more alphanumeric characters to be matched zero or more times.
  • \.[a-z]{2,6} - A dot followed by between two and six letters.
  • $ - End of string.

JavaScript test:

var fqdn = "aws.logs.security.stark.tony.com";
if (fqdn.match(/^(?:\*\.)?[a-z0-9]+(?:[\-.][a-z0-9]+)*\.[a-z]{2,6}$/)) {
    console.log("Matched");
}
else{
    console.log("Not Matched");
}

To support upper-case letters, you can either (re-)add A-Z to the character classes or simply append the i flag at the end:

fqdn.match(/^(?:\*\.)?[a-z0-9]+(?:[\-.][a-z0-9]+)*\.[a-z]{2,6}$/i)
//                                                              ^

Upvotes: 3

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