JSFiddle - React, Tailwind, and code Playground

HTML

<select id="dropdown_test">
    <option>1</option>
    <option>2</option>
    <option>3</option>
    <option>4</option>
</select>
<select id="dropdown_test">
    <option>1</option>
    <option>2</option>
    <option>3</option>
    <option>4</option>
</select>

CSS

.tagging {
    padding:30px;
    background-color:#ccf;
    width : 10px;
    height: 10px;
}
.oldclass {
    color:#f00;
}

JavaScript

var all_select = document.getElementsByTagName("select");
for (i = 0; i < all_select.length; i++) {
    all_select[i].value = 3;
}