Question

in a form, onkeypress, I call this function:

function calculate() {

    var subtotal = parseInt(document.form1.product1.value) * product1 + 
                    parseInt(document.form1.product2.value) * product2 + 
                    parseInt(document.form1.product3.value) * product3;
    alert(typeof subtotal);
    alert(subtotal);
    var total = subtotal + parseInt(document.form1.shipping.value);

    document.form1.subtotal.value = subtotal;
    document.form1.total.value = total;
}

When I alert the typeof subtotal, I get number. But then when I alert the subtotal, I get NaN. What am I missing? Thanks.

Answer 1

When I alert() the typeof subtotal, I get number.

typeof NaN is number in JavaScript.

But then when I alert the subtotal, I get NaN.

NaN is toxic, if it is part of any arithmetic, the result is NaN.

The most probable reason is that parseInt() is returning NaN. Are those elements’ value property an empty string?