JSFiddle - React, Tailwind, and code Playground

HTML

<select id="meu_select"></select>
<input id="botao_1" type="button" value="2" />
<input id="botao_2" type="button" value="B" />

JavaScript

var select = document.getElementById('meu_select');
var botao_1 = document.getElementById('botao_1');
var botao_2 = document.getElementById('botao_2');

botao_1.onclick = function() {
    select.innerHTML = '<option>1</option><option selected="selected">2</option>';
}

botao_2.onclick = function() {
    select.innerHTML = '<option>A</option><option selected="selected">B</option><option>C</option>';
}