The JavaScript function replaces all occurrences of the "&" character in the text content of all elements in the document with the HTML entity "&".

ampersands.js

document.addEventListener('DOMContentLoaded', () => {
  Array.from(document.querySelectorAll('*:contains("&")')).forEach((elem) => {
    Array.from(elem.childNodes).forEach((node) => {
      if (node.nodeType === Node.TEXT_NODE) {
        const newNode = document.createElement('span');
        newNode.className = 'amp';
        newNode.textContent = node.textContent.replace(/&/g, '&');
        node.parentNode.replaceChild(newNode, node);
      }
    });
  });
});

style.css

span.amp {
    font-family: Baskerville, "Baskerville Old Face", "Hoefler Text", Garamond, "Times New Roman", serif;
    font-style: italic;
    font-weight: normal;
}