防止在Firefox中选择/复制到剪贴板

document.addEventListener('copy', function(event) {
  event.preventDefault();
  alert('复制和粘贴已被禁用！');
});

document.addEventListener('cut', function(event) {
  event.preventDefault();
  alert('剪切已被禁用！');
});

document.addEventListener('paste', function(event) {
  event.preventDefault();
  alert('粘贴已被禁用！');
});

body {
  -webkit-user-select: none;
  -moz-user-select: none;
  -ms-user-select: none;
  user-select: none;
}