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    <input type="checkbox" id="check">

    const check = document.getElementById('check');
  
    // get state of checkbox from URL parameter
    check.checked = new URLSearchParams(location.search).get('state') === 'on';
    
    // add event listener to call history api to alter the URL state.
    check.onchange = () => { history.replaceState(null, '', check.checked ? '?state=on' : '?state=off'); };