css怎么设置滚动条宽度

.visible-scrollbar, .invisible-scrollbar, .mostly-customized-scrollbar {

  display: block;

  width: 10em;

  overflow: auto; 

  height: 2em;

  }

  .invisible-scrollbar::-webkit-scrollbar {

  display: none;

  }

  /* Demonstrate a "mostly customized" scrollbar

 * (won't be visible otherwise if width/height is specified) */

 .mostly-customized-scrollbar::-webkit-scrollbar {

  width: 5px; 

  height: 8px; 

  background-color: #aaa;

  /* or add it to the track */}/* Add a thumb */

  .mostly-customized-scrollbar::-webkit-scrollbar-thumb {

    background: #000;

    }