Removes all classes and ids from HTML that do not affect styling

removeUnused.js

// Returns e as HTML string 
function serialize(e) {
  const s = new XMLSerializer();
  return s.serializeToString(e);
}

// Recursively removes all classes and ids that do not affect styling from element e
function removeUnused(e) {
  const s0 = window.getComputedStyle(e).cssText;
  const c = Array.from(e.classList.values());
  if (c.length !== 0) {
    c.forEach(cc => {
      e.classList.remove(cc);
      const s = window.getComputedStyle(e).cssText;
      if (s0 !== s) {
        e.classList.add(cc);
      }
    });
  }
  if (e.classList.length === 0) {
    e.removeAttribute("class");
  }
  const id = e.id;
  if (id) {
    e.removeAttribute("id");
    const s = window.getComputedStyle(e).cssText;
    if (s0 !== s) {
      e.id = id;
    }
  }
  Array.from(e.children).forEach(removeUnused);
}

// outputs unused classes, ids in e
function logUnused(e) {
  const s0 = window.getComputedStyle(e).cssText;
  const c = Array.from(e.classList.values());
  if (c.length !== 0) {
    c.forEach(cc => {
      e.classList.remove(cc);
      const s = window.getComputedStyle(e).cssText;
      if (s0 === s) {
        console.log(`class ${cc} is unused`);
      }
      e.classList.add(cc);
    });
  }
  const id = e.id;
  if (id) {
    e.removeAttribute("id");
    const s = window.getComputedStyle(e).cssText;
    if (s0 === s) {
      console.log(`id ${id} is unused`);
    }
    e.id = id;
  }
}

const d0 = serialize(document.documentElement);
removeUnused(document.documentElement);
const d1 = serialize(document.documentElement);