JSFiddle - React, Tailwind, and code Playground

HTML

<select id="select">
    <option>Number List</option>
    <option id="first">number 1</option>
    <option id="second">number 2</option>
    <option id="third">number 3</option>
</select>

<div>
    <div class="passive" id="first-i">number 1 content</div>
    <div class="passive" id="second-i">number 2 content</div>
    <div class="passive" id="third-i">number 3 content</div>
</div>

CSS

.passive {
    display: none;
}

.active {
    display: block;
}

JavaScript

var select = document.getElementById('select'),
    curr = null;

select.addEventListener('change', function() {

    var name   = this.options[this.selectedIndex].getAttribute('id'),        
        target = document.getElementById(name + '-i');
    
    if (curr) curr.className = 'passive';
    if (target) target.className = 'active';
    curr = target;
});