JSFiddle - React, Tailwind, and code Playground

HTML

<input id="price_lvl" placeholder="LVL">
<input id="price_eur" placeholder="EUR">

JavaScript

$(function() {
    $("#price_lvl").blur(function() {
        lvl = parseFloat($('#price_lvl').val().replace(",", "."));
        eur = 0;
        if (lvl > 0) {
            eur = lvl * 0.702804
        }            
        eur = parseFloat(Math.round(eur * 100) / 100).toFixed(2)
        $("#price_eur").val(eur);
    });
});