Take the rest of the decimal places and perform a conversion

Question

I am very layman in javascript, but I think you can do this in this language. I tried it in a very trivial way, but I did not succeed. Basically I have a system that converts the amount into kg for boxes of cookies, for example:

function bisc_salg(){
	p3 = document.getElementById("multiplicando3").value;
	p4 = document.getElementById("multiplicador3").value;
	r = p3/p4;
	document.getElementById("resultado3").value = r.toFixed(3);
	}

<form id="bisc_salg" class="box_Branco">
<p class="desc_item"> Biscoito Salgado Cream Cracker </p>
  <input type="text" placeholder="Qtde." class="qtde_Req" id="multiplicando3" onChange="bisc_salg();"> 
  <input type="text" class="invisible" id="multiplicador3" readonly="readonly" value=4.8 onChange="bisc_salg();"> =
  <input type="text" class="retorno" id="resultado3" readonly="readonly"> caixas
</form>

Let’s assume that I have 14.8 kg and playing in this system I get: 3,083 which means 3 whole boxes and a packet of biscuits. That is, each package has 400 grams. How do I take this rest of the decimal place and convert into packages? More or less would have to return:

3 boxes and 1 package.

The summary data are: Each box has 12 packets of cookies and 4.8 Kg; each cookie has 400 grams.

Answer 1

You can use the module operator % that returns the rest of the division...

9 % 3 // retorna 0
10 % 3 // retorna 1
11 % 3 // retorna 2
12 % 3 // retorna 0

So if you divide the result of the module by the weight of the package (0.4kg) you will have the amount of packages...

console.log('pacotes:', Math.round(14.8 % 4.8 / 0.4));
console.log('pacotes:', Math.round(15.2 % 4.8 / 0.4));

The Math.round is because of the error of splitting with floating points... See more here