JSFiddle - React, Tailwind, and code Playground

HTML

<div id="phrases">Фраза 1, Фраза 2, Фраза 3</div>

<div id="test"></div>

JavaScript

const SITE_URL = "http://site.ru";
const CONTAINER = document.getElementById("test");

let links = document.getElementById('phrases')
  .innerHTML
  .split(", ")
  .map(phrase => makeLink(SITE_URL, phrase));

links.forEach(function(link, index) {
  CONTAINER.appendChild(link);

  if (!isLastItem(links, index)) {
    CONTAINER.appendChild( textNode(", ") );
  }
});

function makeLink(site, text) {
  let a = document.createElement("a");

  a.innerHTML = text;
  a.href = `${site}/${text}`;

  return a;
}

function isLastItem(array, index) {
  return index === array.length - 1;
}

function textNode(text) {
  return document.createTextNode(text);
}