javascript updatesum() problems

Question

I have the following JavaScript code which is writing in a HTML form:

  <script type="text/javascript">
    function updatesum() {
    document.functie.column8.value = (document.functie.column6.value -0) * (document.functie.column7.value -0);
    document.functie.column12.value = (document.functie.column10.value -0) * (document.functie.column11.value -0);
    document.functie.column16.value = (document.functie.column14.value -0) * (document.functie.column15.value -0);
    document.functie.column20.value = (document.functie.column18.value -0) * (document.functie.column19.value -0);
   }

and with the php form like:

echo "<td><input name=\"column6\" onChange=\"updatesum()\"></td>";
echo "<td><input name=\"column7\" onChange=\"updatesum()\"></td>";

1. The problem is that when I put some values in the first form, it gives me the sum, but if I don't put some values it gives me zero, which I do not want:

   http://img17.imageshack.us/img17/5456/hyhu.png http://img17.imageshack.us/img17/5456/hyhu.png

2. In the bottom I have a sum of all the values from the 3rd column, but the it gives me numbers like 2400 or 2300.44, and I want an output of 2,400 or to roundup the 2300.44 to 2,300. How can I do that?

Answer 1

1/ You're multiplying with a value '' automatically cast to an integer, so 0. This is normal that you end up with 0. If you do not want that, you'll have to create a function that check the value of the inputs and return '' if one of them is '' something like:

function multiply(v1, v2) {
    if (v1 === '' || v2 === '' || isNaN(v1) || isNaN(v2)) {
        return '';
    } 
    return v1*v2;
}

2/ You'll need to add a format function, that will format your code and add the , where it must and get ride of the decimals (or use links in that comment javascript updatesum() problems) :

function formatNumber(num) {
    var formatted = '';
    num = Math.ceil(num) + '';
    for (var i = num.length - 1, j = 0; c = num.charAt(i); i--) {
        if (j % 3 === 0) {
            c = c + ',';
        }
        formatted = c + formatted;
        j++;
    }
    return formatted.trim();
}

You asked for an example. This should do it in place of your current updatesum function:

function multiply(v1, v2) {
    if (v1 === '' || v2 === '' || isNaN(v1) || isNaN(v2)) {
        return '';
    } 
    return v1*v2;
}
function multiplyAndFormat(v1, v2) {
    return formatNumber(multiply(v1, v2));
}

function formatNumber(num) {
    var formatted = '';
    num = Math.ceil(num) + '';
    for (var i = num.length - 1, j = 0; c = num.charAt(i); i--) {
        if (j % 3 === 0) {
            c = c + ',';
        }
        formatted = c + formatted;
        j++;
    }
    return formatted.trim();
}

function updatesum() {
    document.functie.column8.value = multiplyAndFormat(document.functie.column6.value, document.functie.column7.value);
    document.functie.column12.value = multiplyAndFormat(document.functie.column10.value, document.functie.column11.value);
    document.functie.column16.value = multiplyAndFormat(document.functie.column14.value, document.functie.column15.value);
    document.functie.column20.value = multiplyAndFormat(document.functie.column18.value, document.functie.column19.value);
}

should do it