Máscara para CPF e CNPJ em javascript utilizando ES6

es6_mask_cpf_cnpj.js

const mask = (v) => {
    v=v.replace(/\D/g,"")
    let len = v.length
    if (len < 12) {
        v=v.replace(/(\d{3})(\d)/,"$1.$2")
        .replace(/(\d{3})(\d)/,"$1.$2") 
        .replace(/(\d{3})(\d{1,2})$/,"$1-$2")
    } else { 
        v=v.replace(/^(\d{2})(\d)/,"$1.$2")
        .replace(/^(\d{2})\.(\d{3})(\d)/,"$1.$2.$3")
        .replace(/\.(\d{3})(\d)/,".$1/$2")
        .replace(/(\d{4})(\d)/,"$1-$2")
    }
    return v.substring(0,18)
}