Cookieを保存する

function setCookie(name, value, day, path, domain) {
  return document.cookie = encodeURIComponent( name ) + '=' + encodeURIComponent( value ) +
  '; ' + 'expires=' + new Date( (new Date) - 86400000 * -day ).toUTCString() +
  '; ' + ( path ? 'path=' + encodeURI( path ) + '; ': '' ) +
  ( domain ? 'domain=' + encodeURI ( domain ) + '; ': '');
}