Trying to redirect user on valid contact form submission

Question

Hi so I'm trying to make my page redirect to 'confirmationpage.html' only when all the fields are correctly entered. This is my Javascript, how would I go about doing this?

const form = document.getElementById('form');
const name = document.getElementById('name');
const email = document.getElementById('email');
const subject = document.getElementById('subject');
const text = document.getElementById('text');

form.addEventListener('submit', function(e) {
e.preventDefault();

checkInputs();
});

function checkInputs() {
// get values from the inputs
const nameValue = name.value.trim();
const emailValue = email.value.trim();
const subjectValue = subject.value.trim();
const textValue = text.value.trim();

if(nameValue === '') {
// show error message
// add error class
setErrorFor(name, 'Name cannot be blank');
} else {
// add success class
setSuccessFor(name);
}

if(emailValue === '') {
setErrorFor(email, 'Email cannot be blank');
} else if(!isEmail(emailValue)) {
setErrorFor(email, 'Please enter a valid email address');
} else {
setSuccessFor(email);
}

if(subjectValue === '') {
setErrorFor(subject, 'A subject is required');
} else {
setSuccessFor(subject);
}

if(textValue === '') {
setErrorFor(text, 'Please add some text');
} else {
setSuccessFor(text);
}
}

function setErrorFor(input, message) {
const formControl = input.parentElement; // .form-control
const small = formControl.querySelector('small');

// add error message
small.innerText = message;

// add error class
formControl.className = 'form-control error';
}
function setSuccessFor(input) {
const formControl = input.parentElement;
formControl.className = 'form-control success';
}

function isEmail(email) {
return /^(([^<>()[\]\\.,;:\s@"]+(\.[^<>()[\]\\.,;:\s@"]+)*.test(email);
}

Any help would be very appreciated! I'm very new to webpage design and I've been struggling a lot recently