How to Input a Discount Price in Javascript?

Question

The Discount field does not register
(discount is supposed to subtract from Grand Total)( check discount sample )

check the the jsfiddle click here

I want it to act like this picture. (with the discount being manually inputed) http://i.dailymail.co.uk/i/pix/2013/02/07/article-2275089-17694138000005DC-460_634x497.jpg

Javascript

function recordToFilename() {
        var input = document.getElementById('discountvalue'),
    discount12 = input.value;

Answer 1

Change your button to

<input type="button" onclick="recordToFilename();" value="Submit Discount"  />

And function

function recordToFilename() {
            var input = document.getElementById('discount'),
        discount12 = input.value;

alert (discount12);
}

Answer 2

you have 2 id="discount". Change one of the id and the there is no problem to register the input value to discount12.

Put this line document.getElementById('discounts').innerHTML = "<strong>Discount </strong>: $" + (salesTotal * 0.14 + salesTotal - discount12).toFixed(2); in your recordToFilename() method and make sure your variable is chage to discount12 not discount