JSFiddle - React, Tailwind, and code Playground

HTML

<select size="3" multiple="multiple">
<option selected="selected">One</option>
<option selected="selected">Two</option>
<option selected="selected">Three</option>
</select>

<button>Unselect "Two"</button>

JavaScript

$("button").click(function() {
    var $select = $("select"),
        values = $select.val(),
        index = values.indexOf("Two");
    
    if (index != -1) values.splice(index, 1);
    $select.val(values);
    
});