Calculate subtotal even if all fields are not filled

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I have a form where procedures values need to be entered to be calculated at the end, but values are not always entered in all fields. I wanted to know how validation for the procedure total exits even if values are entered only in two fields for example. Also, the calculation is not coming out after the comma. For example: if I put 12.50 + 12.50 it only leaves 24 and not 25.00

    
asked by anonymous 17.05.2018 / 14:37

1 answer

1

In general I did a routine that can be easily adapted to any type of operation and amount of fields.

Just add the fields, retrieve the values and make the proper calculations on the variable total 

  //formata o resultado para reais e decimais com virgula
  function reais(n) {
    var l = Math.floor(n);
    var r = Math.round((100*n)%100);
    if (r<10) return "R$"+l+",0"+r;
    if (r==100) return "R$"+(l+1)+",00";
    return "R$"+l+"."+r;
  }

  function calculate(f) {
    //retorno dos valores dos campos
    var id1=document.getElementById('id1').value;
    var id2=document.getElementById('id2').value;
    var id3=Number(document.getElementById('id3').value);
    var id4=document.getElementById('id4').value;
    var id5=document.getElementById('id5').value;
    //para não invalidar o resultado caso haja alguma divisão no total
    if(id5==""){
       id5=1;
    }
    //aqui as operações envolvendo os campos
    var total=(((id1*id2)+id3)-id4)/id5;
    f.total.value=reais(total);

  }
<form>
  Quantidade 
  <input type="text" name="input1"t id="id1">
  Preço Unitário
  <input type="text" name="input2" id="id2"><br>
  Imposto
  <input type="text" name="input3" id="id3"><br>
  Desconto
  <input type="text" name="input4" id="id4"><br>
  Parcelas
  <input type="text" name="input5" id="id5">

  <p>
  <table>
    <tr><td>
      Resultado:</td><td><input type=text name=total size=8>
    </td></tr>
  </table>
  <p>
  <input type=button value=Calculate onClick="calculate(this.form);"> 
</form>
  

The + operator may surprise you depending on the way you use it.

  • Everyone knows that the + operator serves for at least two things: adding numbers and concatenating strings!
  • In the example of the response the variable var id3 was transformed into a number with the function Number to perform the addition operation because otherwise there would be a concatenation.
  

Instead of using the Number function in the variable var id3 we could use the + operator itself to convert it to a number.

See how:

Instead of: 

var id3=Number(document.getElementById('id3').value);

Use 

var id3=document.getElementById('id3').value;

And replace var total with 

var total=(((id1*id2)+(+id3))-id4)/id5;

Example 

//operador + para conveeter em numero
console.log(10 + +'10');
//sem o operador +
console.log(10 + '10');
    
17.05.2018 / 15:45
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