Example how to make math calculation with safe output

safe_math_operator.js

const countDecimals = function (value) {
    if(Math.floor(value) === value) return 0;
    return value.toString().split(".")[1].length || 0; 
}

const operators = {
    '+': (a, b) => {
        let decimalLength = Math.pow(10, Math.max(countDecimals(a), countDecimals(b)))
        return ((a*decimalLength) + (b*decimalLength))/decimalLength
    },
    '-': (a, b) => {
        let decimalLength = Math.pow(10, Math.max(countDecimals(a), countDecimals(b)))
        return ((a*decimalLength) - (b*decimalLength))/decimalLength
    },
    '*': (a, b) => {
        let decimalLength = Math.pow(10, Math.max(countDecimals(a), countDecimals(b)))
        return ((a*decimalLength) * (b*decimalLength))
    },
    '/': (a, b) => {
        let decimalLength = Math.pow(10, Math.max(countDecimals(a), countDecimals(b)))
        return ((a*decimalLength) / (b*decimalLength))
    },
    '%': (a, b) => {
        let decimalLength = Math.pow(10, Math.max(countDecimals(a), countDecimals(b)))
        return ((a*decimalLength) % (b*decimalLength))
    },
}

//Example
// 0.1+0.2 = 0.30000000000000004
// With this you will get 0.3
console.log(operators['+'](0.1, 0.2))