function format (lang, currency, number) {
  return new Intl.NumberFormat(lang, { style: "currency", currency }).format(number);
} 

function reverseFormat(lang, currency, money) {
  const separatorDecimal = new Intl.NumberFormat(lang, {
    style: "decimal"
  })
    .format(11.11)
    .replace(/\d/g, "");

  const separatorThousands = new Intl.NumberFormat(lang, {
    style: "decimal"
  })
    .format(1111)
    .replace(/\d/g, "");

  const symbolOnLeft = new Intl.NumberFormat(lang, {
    style: "currency",
    currency
  })
    .format(1)
    .replace(
      new RegExp(`\\d|[${separatorDecimal}${separatorThousands}]*`, "g"),
      ""
    );

  const stringNumber = money
    .replace(new RegExp(`[${separatorThousands}]`, "g"), "")
    .replace(separatorDecimal, ".")
    .replace(new RegExp(`[${symbolOnLeft}]`, "g"), "");

  return parseFloat(stringNumber);
}



const language = "pt-BR";
const currency = "BRL";

const money = 1234567.89;
const moneyFormated = "R$ 1.234.567,89";

console.log("format", format(language, currency, money));
// >> format R$ 1.234.567,89
console.log("reverseFormat", reverseFormat(language, currency, moneyFormated));
// >> reverseFormat 1234567.89