JSFiddle - React, Tailwind, and code Playground

JavaScript

function soma(a, b, casasDecimais) {
    if (typeof a == 'string') a = parseFloat(a);
    if (typeof b == 'string') b = parseFloat(b);
    var soma = a + b;
    return soma.toFixed(casasDecimais);
}


var res1 = soma(0.4, 0, 1);
var res2 = soma(0.4, res1, 1);
var res3 = soma(0.4, res2, 1);
alert([res1, res2, res3].join(' - '));