Prefill First, Last and Email using JS on WordPress

<script type="text/javascript">
var count = $('input[name*="email"]').length;
var current = 0;
var contactfirst = "[pilotpress_field name='First Name']";
var contactlast = "[pilotpress_field name='Last Name']";
var contactemail = "[pilotpress_field name='Email']";
while (current<count) {
document.getElementsByName('firstname')[current].value = contactfirst;
document.getElementsByName('lastname')[current].value = contactlast;
document.getElementsByName('email')[current].value = contactemail;
current++;
}
</script>