Question

I have a form, with the 3 input type text.

<input type="text" id="one" onkeyup="multiply()" name="one">
<input type="text" id="two" name="two">
<input type="text" id="three" name="three">

<script>
function multiply(){
    one = document.getElementById('one').value;
    two = document.getElementById('two').value;
    document.getElementById('three').value = one * two
}
</script>

now i don’t have value in three, but it is a dynamic one, when i submit forum to (forumSubmit.php)then i get error of

undefiend index three

I searched & found this can be done with ajax, but i don’t want to use ajax, i want to make a page refresh

Answer 1

<input type="text" id="one" onkeyup="multiply()" name="one" />
<input type="text" id="two" onkeyup="multiply()" name="two" />
<input type="text" id="three" name="three" />

<script type="text/javascript">
function multiply() {
    one = document.getElementById('one').value;
    two = document.getElementById('two').value;
    document.getElementById('three').value = one * two;
}
</script>