Example Select

example select multiple

HTML

<select multiple>
  <option>One</option>
  <option>Two</option>
  <option>Three</option>
</select>

JavaScript

const selectElem = document.querySelector('select');
selectElem.onmousedown = function(e) {
  e.preventDefault();
  const st = this.scrollTop;
  e.target.selected = !e.target.selected;
  setTimeout(() => this.scrollTop = st, 0);
  this.focus();
};

selectElem.onmousemove = function(e) {
  e.preventDefault();
};