menghitung angka otomatis

<script type="text/javascript">
    function startCalc(){
        interval=setInterval("calc()",1)}function calc({
                one=document.autoSumForm.firstBox.value;
                two=document.autoSumForm.secondBox.value;document.autoSumForm.thirdBox.value=(one*1)+(two*1)
        }
    function stopCalc(){
        clearInterval(interval)
    }
</script>

<form name="autoSumForm">
<input type=text name="firstBox" value="" onFocus="startCalc();" onBlur="stopCalc();"> +
<input type=text name="secondBox" value="" onFocus="startCalc();" onBlur="stopCalc();"> =
<input type=text name="thirdBox">
</form>

Read more: http://kampungkuini.blogspot.com/2012/06/penjumlahan-otomatis-dengan-javsscrift.html#ixzz3FR5JByho