Как сделать поиск по сайту?

<form action="/">
    <input type="search" name="search">
</form>

<form id="search">
    <input type="search" name="search">
    <button type="submit">OK</button>
</form>

window.onload = function() {
  document.getElementById('search').addEventListener('submit', function(e) {
     e.preventDefault();
     
     let s = this.search.value;
     location.href = "?search=" + s;
  });
};

<form method="GET" action="/">
    <input type="search" name="search">
</form>