Auto calculate the subtraction of total earn and total deduction

JavaScript
1

Good day!

I am new in javascript function.

I have Javascript code for auto calculate

here is the code:


<script type="text/javascript" language="javascript">

function autocalearn(oText)
{
if (isNaN(oText.value)) //filter input
{
alert('Numbers only!');
oText.value = '';
}
var field, val, oForm = oText.form, TotEarn = a = 0;
for (a; a < arguments.length; ++a) //loop through text elements
{
field = arguments[a];
val = parseFloat(field.value); //get value
if (!isNaN(val)) //number?
{
TotEarn += val; //accumulate
}
}
var tot=Number(TotEarn) + Number(document.getElementById('Amount').value);
oForm.TotEarn.value = tot.toFixed(2);
//oForm.TotEarn.value = TotEarn.toFixed(2); //out
 
}

</script>
<!--Total Deduction AutoCompute-->
<script type="text/javascript" language="javascript">

function autocalded(oText)
{
if (isNaN(oText.value)) //filter input
{
alert('Numbers only!');
oText.value = '';
}
var field, val, oForm = oText.form, TotalDed = a = 0;
for (a; a < arguments.length; ++a) //loop through text elements
{
field = arguments[a];
val = parseFloat(field.value); //get value
if (!isNaN(val)) //number?
{
TotalDed += val; //accumulate
}
}
//oForm.TotalDed.value = TotalDed.toFixed(2); //out

var totded=Number(TotalDed) + Number(document.getElementById('Deductions').value);
oForm.TotalDed.value = totded.toFixed(2);
}

</script>

and now my problem is…I have a textbox for the overall total, and i want it automatic subtract the total earn and total deduction…

I will attach my codes for further understanding.

Thank you in advance