Czytanie bioniczne — pogrubione początki słów

(function () {
  var article = document.querySelector('article, .post, .entry-content, main');
  if (!article) return;
  var walker = document.createTreeWalker(article, NodeFilter.SHOW_TEXT);
  var nodes = [];
  while (walker.nextNode()) nodes.push(walker.currentNode);
  nodes.forEach(function (node) {
    if (!node.nodeValue || !node.nodeValue.trim()) return;
    if (node.parentNode && /SCRIPT|STYLE|CODE|PRE/.test(node.parentNode.nodeName)) return;
    var frag = document.createDocumentFragment();
    node.nodeValue.split(/(\s+)/).forEach(function (part) {
      if (!part.trim()) { frag.appendChild(document.createTextNode(part)); return; }
      var cut = Math.max(1, Math.ceil(part.length * 0.4));
      var b = document.createElement('b');
      b.textContent = part.slice(0, cut);
      frag.appendChild(b);
      frag.appendChild(document.createTextNode(part.slice(cut)));
    });
    node.parentNode.replaceChild(frag, node);
  });
})();