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Calculating Sum Of 2 Form Fields Using Javascript

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        Automatically adds two fields together (text fields), without the need for a submit or input button.

<script type="text/javascript"><!--
function updatesum() {
document.form.sum.value = (document.form.sum1.value -0) + (document.form.sum2.value -0);


<form name="form" >
Enter a number:
<input name="sum1" onChange="updatesum()" />
and another number:
<input name="sum2" onChange="updatesum()" />
Their sum is:
<input name="sum" readonly style="border:0px;">