如何阻止文本被选中？

body {
  -webkit-user-select: none; /* Chrome, Safari, Opera */
  -moz-user-select: none; /* Firefox */
  -ms-user-select: none; /* Internet Explorer/Edge */
  user-select: none; /* Non-prefixed version, currently supported by Chrome and Opera */
}

body {
  -webkit-user-drag: none; /* Chrome, Safari, Opera */
  -moz-user-drag: none; /* Firefox */
  -ms-user-drag: none; /* Internet Explorer/Edge */
  user-drag: none; /* Non-prefixed version, currently supported by Chrome and Opera */
}

document.addEventListener('selectstart', function(e) {
  e.preventDefault();
});