prev page js

const prevPage = document.referrer
if (origin(createAnchor(prevPage)) === origin(window.location)) {
  window.history.pushState(location.href, '', '/')
} else {
  window.history.back()
}

function createAnchor(url) {
  const anchor = document.createElement('a')
  anchor.href = url
  return anchor
}

function origin(loc) {
  var protocol = (loc.protocol && ':' !== loc.protocol) ? loc.protocol : location.protocol
  var host = [loc.hostname, parseInt(loc.port, 10) === 80 ? 0 : loc.port].filter(Boolean).join(":")
      || [location.hostname, parseInt(location.port, 10) === 80 ? 0 : location.port].filter(Boolean).join(":")
  return protocol + "//" + host
}