increase thai font size

increase-thai-font-size.mjs

(() => {
  // Styles to apply
  const styles = {
    fontSize: '30px',
    fontFamily: '"Noto Serif Thai", serif',
  }

  // Add fonts if they don't exist
  const font_url = "https://fonts.googleapis.com/css2?family=Noto+Serif+Thai&display=swap";
  if (!document.head.querySelector(`link[href="${font_url}"]`)) {
    document.head.innerHTML += `<link href="${font_url}" rel="stylesheet">`;
  }

  // Look for these Characters
  const chars = "กขฃคฅฆงจฉชซฌญฎฏฐฑฒณดตถทธนบปผฝพฟภมยรลวศษสหฬอฮ".split("");

  function resize_thai_script() {
    // List of elements with Thai characters in them
    const elements_to_update = new Set();

    // Scan the page for elements that contain those characters
    (function walk_elements(target) {
    for (const el of Array.from(target.querySelectorAll("*"))) {
        // Custom Elements
        if (el.shadowRoot) {
        walk_elements(el.shadowRoot);
        }

        // Only look at the text of the current element and not the children
        let top_level_text = "";

        for (var i = 0; i < el.childNodes.length; i++) {
        if (el.childNodes[i].nodeType == Node.TEXT_NODE) {
            top_level_text += el.childNodes[i].data;
        }
        }

        // does the top level text contain any Thai characters?
        for (const char of chars) {
        if (top_level_text.includes(char)) {
            elements_to_update.add(el);
            break;
        }
        }
    }
    })(document.body);

    // Apply styles to found elements
    for (const el of elements_to_update.values()) {
      for (const [k, v] of Object.entries(styles)) {
        el.style[k] = v
      }
    }
  }

  resize_thai_script()

  // Automatically run whenever there are changes to the page
  if (window.thai_observer) {
    window.thai_observer.disconnect()
  }
  window.thai_observer = new MutationObserver(() => resize_thai_script())
  window.thai_observer.observe(document.body, { 
    attributes: false,
    childList: true,
    characterData: true,
    subtree: true,
  });
})();