<!DOCTYPE html>
<html>
<body>

A hidden input field:
<input type="hidden" id="myInput" name="country" value="Norway">

<p>Click the buttons to display and/or change the value of the name attribute of the hidden input field.</p>

<button onclick="display()">Display name</button>
<button onclick="change()">Change name</button>

<script>
function display() {
    var x = document.getElementById("myInput").name;
    alert("The name of the hidden input field is: " + x);
}

function change() {
    var x = document.getElementById("myInput").name = "newName";
    alert ("The name was changed to: " + x);
}
</script>

</body>
</html>