const regex = /^[A-zÀ-ÿ ]*\1*,(?:\s)(\w*,\s)(CEP (\d{5}-\d{3}))/gim;
// Alternative syntax using RegExp constructor
// const regex = new RegExp('^[A-zÀ-ÿ ]*\\1*,(?:\\s)(\\w*,\\s)(CEP (\\d{5}-\\d{3}))', 'gim')
const str = `Rua das Flores, 123, CEP 60321-105
Avenida Brasil, 456A, CEP 16945-017
Travessa dos Santos, 101, CEP 12345-678
Rua Catarina, 243, CEP 25437-987
Rua Sâo Pedro, 243, cep 25437-987
`;
const subst = `\^[A-Za-z ]*\1*,(?:\s)(\w*,\s)(CEP (\d{5}-\d{3}))\`;
// The substituted value will be contained in the result variable
const result = str.replace(regex, subst);
console.log('Substitution result: ', result);
Please keep in mind that these code samples are automatically generated and are not guaranteed to work. If you find any syntax errors, feel free to submit a bug report. For a full regex reference for JavaScript, please visit: https://developer.mozilla.org/en/docs/Web/JavaScript/Guide/Regular_Expressions