JSFiddle - React, Tailwind, and code Playground

HTML

<input id="n" valude=""/>

JavaScript

/*Numero a formatear*/
var NUM = 3500;

function format1(n, currency) {
    return currency + " " + n.toFixed(2).replace(/./g, function(c, i, a) {
        return i > 0 && c !== "." && (a.length - i) % 3 === 0 ? "," + c : c;
    });
}
var salida = format1(NUM,"Bs.");
document.getElementById('n').value = salida;