x
 
<!DOCTYPE html>
<html>
<head>
<style>
::file-selector-button {
  border: 2px solid black;
  padding: 5px 10px;
  border-radius: 5px;
  background-color: lightgreen;
}
::file-selector-button:hover {
  background-color: salmon;
  cursor: pointer;
}
</style>
</head>
<body>
<h1>::file-selector-button 演示</h1>
<form>
  <label for="fileUpload">上传文件:</label>
  <input type="file" id="fileUpload" />
</form>
</body>
</html>