How can I re-validate a email address in a Eloqua form using javascript

Hello,

I'd like to have the new lead re-enter their email address into a form a second time to ensure the first entry is correct. I 've added an additional form field to capture the email value (a second time). I'm hoping someone as implemented a solution for this already. Assuming this will require custom javascript code I'll need help with this as I'm not comfortable with the HTML/script in the form. I put some sample code below, that may help to match the values. But I'm sure someone has an elegant solution for this already. Please advise.

var firstEmailInput = document.getElementById("first").value;