Formatar moeda no valor $ americano para R$ real.

formatMoney.js

function formatMoney(n, c, d, t) {
  c = isNaN(c = Math.abs(c)) ? 2 : c, d = d == undefined ? "," : d, t = t == undefined ? "." : t, s = n < 0 ? "-" : "", i = parseInt(n = Math.abs(+n || 0).toFixed(c)) + "", j = (j = i.length) > 3 ? j % 3 : 0;
  return s + (j ? i.substr(0, j) + t : "") + i.substr(j).replace(/(\d{3})(?=\d)/g, "$1" + t) + (c ? d + Math.abs(n - i).toFixed(c).slice(2) : "");
}
console.log(formatMoney(600000.00));
console.log(formatMoney(10));
console.log(formatMoney(100));
console.log(formatMoney(0.5));
console.log(formatMoney(1500));
console.log(formatMoney(89));