JSFiddle - React, Tailwind, and code Playground

HTML

<form action="">
   <select id="id_get" name="name" multiple="multiple">
   <option selected="selected" value="a">A</option>
   <option selected="selected" value="b">B</option>
   </select>
   <select id="id_set" name="name" multiple="multiple">
   <option value="a">A</option>
   <option value="b">B</option>
   </select>

</form>

JavaScript

console.log(document.getElementById('id_get').value)
document.getElementById('id_set').value = ['a', 'b']