javascript - Display vat value in text box

Question

Does anyone know why I'm getting a value NaN in the vat input box? When I enter a value of qty it always gives me a NaN value.

$('#sales_qty').keyup(function(){
    var qty = parseFloat($('#sales_qty').val()) || 0;
    var sub_total = parseFloat($('#sales_sub_total').val()) || 0;
    var vat = 0.12;

    var sales_total = $('#sales_total').val((qty * sub_total).toFixed(2));

    $('#sales_vat').val((sales_total * vat).toFixed(2));
});

JSFiddle: https://jsfiddle.net/yv6zks1g/

question from:https://stackoverflow.com/questions/65651798/display-vat-value-in-text-box

Answer 1

Because sales_total is the element itself, (not the value). you should add another val() at the end to get the value.

$('#sales_qty').keyup(function(){
    var qty = parseFloat($('#sales_qty').val()) || 0;
    var sub_total = parseFloat($('#sales_sub_total').val()) || 0;
    var vat = 0.12;

    var sales_total = $('#sales_total').val((qty * sub_total).toFixed(2)).val();

    $('#sales_vat').val((sales_total * vat).toFixed(2));
});

<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script>
<input id="sales_qty" type="text" placeholder="sales_qty" />
<input id="sales_sub_total" type="text" placeholder="sales_sub_total" />
<input id="sales_total" type="text" placeholder="sales_total" />
<input id="sales_vat" type="text" placeholder="sales_vat"/>