dropdown is not scroll with selection using keyboard

[chiragsatapara]

I add below css into the code and put a scroll bar. when i select using a keyboard and on down , when i read to the next element but scrollbar is not automatic down , i have to down using mouse then i can see the selected option in to the dropdown. see screenshot.

.dropdown {
  position: absolute;
  top: 100%;
  min-width: 150px;
  right: 0;
  max-height: 300px;
  overflow: auto; 
  background: lightblue;
  list-style: none;
  padding: 0;
  margin: 0; }