JSFiddle - React, Tailwind, and code Playground

HTML

<form id="formulario">
        <fieldset>
        <legend>Validação e Formatação</legend>
        <label for="cpf">CPF:<label>
        <input name="cpf" type="text" />

        <label for="email">Email:<label>
        <input name="email" type="text" />

        <a href="#" onclick="validar()">Validar</a>
        </fieldset>
  </form>

JavaScript

validar = function () {
    var formulario = document.getElementById("formulario");
    var cpf = formulario.cpf;
    var email = formulario.email;
    var re_cpf = /^([\d]{3})([\d]{3})([\d]{3})([\d]{2})$/;
    var re_email = /^([\w\.\-]+)@([\w\-]+)((\.(\w){2,3})+)$/;   

    if(re_cpf.test(cpf.value)){
        alert("CPF válido");}
        else{
            alert("CPF inválido");
    }
    
    if(re_email.test(email.value)) alert('E-mail válido');
    else alert('E-mail inválido');
}