Sum inputs checkbox and at the end subtract one

Question

I rephrased that question, I’ll try to be more objective. I have that field on the form:

Where the area code you calculate is this:

  $( "div#molhos :checkbox:checked" ).each(function() {
            sub += $( this ).val() * $( this ).parent().find("select").val();

}); // each molhos

So far so good, what I need is that at the end of the calculation it subtracts ONE, example: If the user chooses THREE SAUCE 1 and TWO SAUCE 3 the total will be 5 sauces, correct? It would be R $ 7,50, but I want the result always stay with LESS ONE, would be the right amount R $ 6,00.

The Rule would be, choosing ONE sauce only, comes out for free, from the second we will charge.

I don’t know if it helps, but there’s more code information: It gets me to the top:

var str = "";
var id = "";
var sub = 0.00;
var taxa = 0;
var taxadeentrega = total - taxa;
var total = 0.00;
var qcount = 0;
var scount = 0;
var opc = 0;
var options = "";
for (i=1; i<21; i++){
    options += "<option value='" + i + "'>" + i + "</option>";
}

This is another area of code that is mentioned the Sauce:

<!--MOLHOS-->

        $( "div#molhos :checkbox:checked" ).each(function() {
              var sel = $(this).parent().children("select").val();
              str = str + $(this).parent().children("strong").text() + ": R$ " + $(this).val().replace(".", ",") + " x " + sel + " = R$ " + (($(this).val() * sel).toFixed(2)).replace(".", ",") + "<br>";
        })
        $('input[name=molhos]').val(str);
        str = "";

But I believe that the important part to create this rule is the first of this post! I believe it is the Rule if, but I can not do, tried everything!!

Answer 1

So I understand your difficulty is in making the total calculation of the sauces, so it follows the code, basically from the last part.

var totalMolhos = 0;
var gratisQtd = 1;
var valorMolhoUnidade = 1.50;
var valorTotalMolhos = 0;
$( "div#molhos :checkbox:checked" ).each(function(i) {
    $totalMolhos = $( this ).val() * $('campo_com_a_quantidade_do_molho').val();
}); // each molhos

if(totalMolhos>0){
    /*aqui é so subtrair do total a quantidade de molhos gratis, no seu caso 1*/
    valorTotalMolhos = (totalMolhos-gratisQtd) * valorMolhoUnidade;
}

Answer 2

I imagine that solves your problem:

$('#molhos input[type="checkbox"]').change(function() {

    var count = $('#molhos input[type="checkbox"]:checked').length;
    count = count == 0 ? 0 : count-1;
  
    var result = 1.50*count;
  
    $('#total').html('Total a pagar nos molhos R$ ' + result);
});

<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>

<div id="molhos">
  
  <div>
    <input type="checkbox" value="1"> Molho 1: R$ 1,50
  </div>
  
  <div>
    <input type="checkbox" value="2"> Molho 2 R$ 1,50
  </div>
  
  <div>
    <input type="checkbox" value="3"> Molho 3 R$ 1,50
  </div>
  
  <div>
    <input type="checkbox" value="4"> Molho 4 R$ 1,50
  </div>
  
</div>

<div id="total"></div>

Every time a checkbox is changed i run the function to calculate the number of selected sauces and display the message pro user accordingly, but remember that it is important to perform an additional check on the server side!

Answer 3

When you give a Get at the value the user entered on the screen, do a check... if the entered value is > 1 you charge for the informed quantity -1.

Ex:

if($_POST['qtdeMolhos'] > 1){
    $valor = 1.5*($_POST['qtdeMolhos']-1);
}else{
    $valor = 0;
}

Did you understand? If it informs 1 the value will be R $ 0,00 and any value greater than this, it multiplies the base value R $ 1,50 by the amount informed less the amount that the house has as courtesy.