npm install --save number-locale-string
const numberLocal = require('number-locale-string');
let value = 1200.00;
// valueString = '1.200'
let valueString = numberLocal.toLocaleString(value, 'pt-BR');
// currencyString = R$1.200,00
let currencyString = numberLocal.toLocaleString(value, 'pt-BR', { style: 'currency', currency: 'brl' });