const regex = /\b((?=[a-z0-9-]{1,63}\.)(xn--)?[a-z0-9]+(-[a-z0-9]+)*\.)+[a-z]{2,63}\b/gm;
// Alternative syntax using RegExp constructor
// const regex = new RegExp('\\b((?=[a-z0-9-]{1,63}\\.)(xn--)?[a-z0-9]+(-[a-z0-9]+)*\\.)+[a-z]{2,63}\\b', 'gm')
const str = `example.com
sub.eample.com
sub-dash.example.com
sub.sub2-dash.example.com
sub.example-dash.com
sub123.example.com
sub.sub123.example.com
www.thisislongerthansixtyonecharacterswhichisnotallowedbythestandards.com`;
// Reset `lastIndex` if this regex is defined globally
// regex.lastIndex = 0;
let m;
while ((m = regex.exec(str)) !== null) {
// This is necessary to avoid infinite loops with zero-width matches
if (m.index === regex.lastIndex) {
regex.lastIndex++;
}
// The result can be accessed through the `m`-variable.
m.forEach((match, groupIndex) => {
console.log(`Found match, group ${groupIndex}: ${match}`);
});
}
Please keep in mind that these code samples are automatically generated and are not guaranteed to work. If you find any syntax errors, feel free to submit a bug report. For a full regex reference for JavaScript, please visit: https://developer.mozilla.org/en/docs/Web/JavaScript/Guide/Regular_Expressions