正则表达式允许子域

Question

Following regex working fine cases where domain is root domain, but this regex not recognizing sub domains as valid domains:

For example: abc.com is being recognized as valid domain, but if I use ab.bc.com then regex says string is not valid, how can I improve this to supprt ab.bc.com too?

  var reg = /^[a-zA-Z0-9][a-zA-Z0-9-]{1,61}[a-zA-Z0-9]\.[a-zA-Z]{2,}$/;
    if ( !reg.test(the_domain)) 
    {
       alert('has special characters');
    } 
    else 
     {
       alert('no special characters');
     }

Here is the jsfiddle

Answer 1

You can add a quantifier for the xx. pattern, and make it as /^([a-zA-Z0-9][a-zA-Z0-9-]{0,61}[a-zA-Z0-9]\\.)+[a-zA-Z]{2,}$/

 var reg = /^([a-zA-Z0-9][a-zA-Z0-9-]{0,61}[a-zA-Z0-9]\\.)+[a-zA-Z]{2,}$/; // ^ ^ changes made console.log(reg.test("abc.com")); console.log(reg.test("ab.bc.com")); console.log(reg.test("ab.bc.com")); console.log(reg.test("ab-.bc.com")); 

Answer 2

/^(\\S+\\.\\S+)$/

This makes sure it has at least a word with a period and another word, if it repeats then its fine.

https://jsfiddle.net/3yb1v222/

or to be more restrictive on characters you can just do:

/^[A-Za-z0-9-_&\\?]+(\\.[A-Za-z0-9-_&\\?]+){1,2}/

you can remove the additional special characters if you are excluding the path on any given url, but either way... its the same concept.

https://jsfiddle.net/u7hgabec/