Detecting URLs with Regular Expressions

Your current code fails to match naked URLs, which lack the "http://" prefix. To address this, consider adopting a comprehensive regular expression:

https?:\/\/(www\.)?[-a-zA-Z0-9@:%._\ ~#=]{1,256}\.[a-zA-Z0-9()]{1,6}\b([-a-zA-Z0-9()@:%_\ .~#?&//=]*)

This enhanced expression includes the following features:

• It ensures that URLs start with either "http://", "https://", or nothing.
• It allows for subdomains by including "(www.)" as an optional prefix.
• It supports domain names up to 256 characters in length and top-level domains up to 6 characters.

For those who do not require the HTTP protocol in their matches, an alternative expression is available:

[-a-zA-Z0-9@:%._\ ~#=]{1,256}\.[a-zA-Z0-9()]{1,6}\b([-a-zA-Z0-9()@:%_\ .~#?&//=]*)

To demonstrate the functionality of these expressions, check out the online testing tools at http://regexr.com?37i6s (for the first expression) or http://regexr.com/3e6m0 (for the less restrictive expression).

Here's an example JavaScript implementation using the more comprehensive regular expression:

const expression = /[-a-zA-Z0-9@:%._\ ~#=]{1,256}\.[a-zA-Z0-9()]{1,6}\b([-a-zA-Z0-9()@:%_\ .~#?&//=]*)/gi;
const regex = new RegExp(expression);
const t = 'www.google.com';

if (t.match(regex)) {
  alert("Successful match");
} else {
  alert("No match");
}