RegExp to match comma separated hostnames

Question

The problem

I\'m trying to validate the content of a </code> using JavaScript, So I created a <code>validate()</code> function, which returns <script async src="https://pagead2.googlesyndication.com/pagead/js/adsbygoogle.js"></script> <ins class="adsbygoogle" style="display:block" data-ad-client="ca-pub-5408099190056760" data-ad-slot="7305827575" data-ad-format="auto" data-full-width-responsive="true"></ins> <script> (adsbygoogle = window.adsbygoogle || []).push({}); </script> </div> </div> <div class="fly-panel detail-box" id="flyReply"> <fieldset class="layui-elem-field layui-field-title" style="text-align: center;"> <legend>6条回答</legend> </fieldset> <ul class="jieda" id="jieda"> <li data-id="111" class="jieda-daan"> <a name="item-1111111111"></a> <div class="detail-about detail-about-reply"> <a class="fly-avatar" href=""> <img src="https://www.e-learn.cn/qa/data/avatar/000/00/00/small_000000043.jpg" alt=" 小蘑菇 "> </a> <div class="fly-detail-user"> <a href="" class="fly-link"> <cite> 小蘑菇</cite> </a> <span>(楼主)</span> </div> <div class="detail-hits"> <span>2021-01-07 04:58</span> </div> </div> <div class="detail-body jieda-body photos"> <p> <p>While @dandavis's answer/comment is impressive, lets break it down in to steps.</p> <ol> <li>Get the value from the textarea and <code>trim()</code> leading and ending spaces.</li> <li>Replace all white spaces with a single white space using <code>/\s+/g</code>. meaning find every white space occurring one or more times.</li> <li>Split by <code>,<space></code> or <code><space>,<space></code>. Split returns array.</li> <li>Iterate every array element with filter</li> <li>Check if element is a valid domain. If so return it.</li> </ol> <p><div class="snippet" data-lang="js" data-hide="false"> <div class="snippet-code"> <pre class="snippet-code-js lang-js prettyprint-override"><code>var domains = document.querySelector("textarea").value; domains = domains.trim().replace(/\s+/g, " ").split(/\s?,\s/); var domainsTested = domains.filter(function(element){ if (element.match(/^[a-zA-Z0-9][a-zA-Z0-9-_]{0,61}[a-zA-Z0-9]{0,1}\.([a-zA-Z]{1,6}|[a-zA-Z0-9-]{1,30}\.[a-zA-Z]{2,3})$/)) { return element; } }) document.write(domainsTested.join(" | ")); //this is just here to show the results. document.write("<br />Domainstring is ok: " + (domainsTested.length == domains.length)); //If it's valid then this should be equal.</code></pre> <pre class="snippet-code-html lang-html prettyprint-override"><code><textarea style="width: 300px; height: 100px">www.example.com , example.com, example.ca, example, example.com example.nl www.example, www.exam ple.com, sub.sub.sub.domain.tv, do main.it, sub.domain.tv