JSFiddle - React, Tailwind, and code Playground

HTML

<select id="zivila">
<option value="110,1.24,0,23.09">Piščanja prsa</option>
<option value="18,0.2,3.92,0.88">Paradižnik</option>
<option value="374,1.04,80.43,8.11">Riž</option>
</select>

<select id="kolicina">
<option value="1">100g</option>
<option value="2">200g</option>
<option value="3">300g</option>
</select>

<button>
Izračunaj
</button>

<p id="kalorije">

</p>
<p id="mascobe">

</p>
<p id="oh">

</p>
<p id="beljakovine">

</p>

JavaScript

$('button').click(function()
{
var kolicina=$("#kolicina").val();
var zivilo=$("#zivila" ).val();
var res = zivilo.split(",");
$('#kalorije').text("Kalorije: "+res[0]*kolicina+"kcal");
$('#mascobe').text("Maščobe: "+res[1]*kolicina+"g");
$('#oh').text("Ogljikovi hidrati: "+res[2]*kolicina+"g");
$('#beljakovine').text("Beljakovine: "+res[3]*kolicina+"g");
})