<div id="out"></div>

#out {
  white-space: pre;
}

function checkByImage(src) {
  // антикэщ
  src += (src.includes('?') ? '&' : '?') + Math.random();

  return new Promise(reslove => Object.assign(new Image(), {
    onload: () => reslove(true),
    onerror: () => reslove(false),
    src
  }))
}

async function check(toCheckList) {
  for(const name in toCheckList) {
    out.append(`${name}: `);
    const ok = await checkByImage(toCheckList[name]) ;
    out.append(ok ? 'доступен' : 'недоступен', '\n');
  }
}

check({
  'patreon.com':'https://patreon.com/favicon.ico',
  'boosty.to': 'https://boosty.to/favicon.ico',
  'linkedin.com': 'https://linkedin.com/favicon.ico'
});