Javascript that calculates % of another calculation

**padders01** · 06-11-2015, 12:31 PM

I have code which calculates 8% of the number entered, so for example is in the code below. If you enter "1" in the first box" and "100" in the second box the Total Refund (including 8%) = 108

JavaScript code:

Code:

$(document).ready(function() {
    var sum = 0;
    function calcSum(prevVal) {
        var val1 = $('#val1').val();
        var val2 = $('#val2').val();
        var val3 = $('#val3').val();
        var val4 = $('#val4').val();
        this.sum = parseFloat(val1) * parseFloat(val2) + parseFloat(val3) * parseFloat(val4);
        return this.sum;
    }
    var subAmt = $("#sub"),
        taxAmt = $("#tax"),
        totAmt = $("#total");
    $(".val").each(function() {
        var prevVal = this.value / 1,
            self = this;
        $(this).keyup(function() {
            subAmt.val(calcSum.call(self, prevVal));
            totAmt.val(this.sum + this.sum * parseFloat(taxAmt.val() / 100));
            prevVal = self.value; 
        });
    });
});

http://jsfiddle.net/2k1zr59u/3/

What I would like to do is to calculate 20% of the 8% in the second to the bottom box. So in this example the answer should be 1.60.

Then I would like to show in the total box 106.40 (108 - 1.60).