JSFiddle - React, Tailwind, and code Playground
HTML
<form>
<label="numero">Só número:
<input id="numero" />
</label>
</form>
JavaScript
document.getElementById('numero').addEventListener("keyup", mascara);
function mascara() {
var v = this.value;
console.log(this);
v = v.replace(/\D/g, '');
v = v.replace(/(\d{2})$/, ',$1');
v = v.replace(/(\d)(?=(\d{3})+(?!\d))/g, '$1.');
v = v != '' ? 'R$ ' + v : '';
this.value = v;
}