JSFiddle - React, Tailwind, and code Playground

HTML

<form id="form-to-submit">
    <select multiple="true" name="sel" id="sel">
        <option id="x0_1" value="0">Bacon</option>
        <option value="1">Pickles</option>
        <option id="x0_3" value="2">Mushrooms</option>
        <option value="3">Cheese</option>        
    </select>
</form>
<button id="setValues">Set Values</button>

JavaScript

$("#setValues").click(function() {
    $("#sel").find("option").removeAttr("selected");
    $("#x0_1").prop("selected",true);
    $("#x0_3").prop("selected",true);

});