JSFiddle - React, Tailwind, and code Playground
HTML
<select class="qty">
<option>1</option>
<option>2</option>
<option>3</option>
<option>4</option>
</select>
<select class="qty">
<option>1</option>
<option>2</option>
<option>3</option>
<option>4</option>
</select>
JavaScript
selectedArr = [2, 3];
$.each(selectedArr, function (i, obj) {
console.log(obj + '' + i );
$('.qty:eq(' + i + ') option:eq(' + obj + ')').prop('selected', true);
});