combobox.css

.combobox {
  position: relative;
  display: inline-block;
}

.combobox * {
  -webkit-box-sizing: border-box;
  -moz-box-sizing: border-box;
  box-sizing: border-box;
}

.combobox .list {
  position: relative;
  overflow-y: auto;
  -webkit-overflow-scrolling: touch;
}

.combobox .options {
  margin: 0;
  padding: 0;
  list-style: none;
}

.combobox .label,
.combobox .group-label,
.combobox .option {
  cursor: pointer;
  overflow: hidden;
  text-overflow: ellipsis;
  white-space: nowrap;
  -webkit-user-select: none;
}

.combobox .option {
  display: none;
}

.combobox .option.selectable {
  display: list-item;
}

.combobox .group.empty {
  display: none;
}

.combobox .inner {
  z-index: 10;
  display: none;
  position: absolute;
  width: 100%;
}

.combobox.open .inner {
  display: block;
}

.combobox.south .inner {
  top: 100%;
}

.combobox.north .inner {
  bottom: 100%;
}

.combobox .search {
  display: none;
  width: 100%;
}

.combobox.searchable .search {
  display: block;
}