javascript - Rounding issue in Math.round() & .toFixed()

Question

I used below two methods :

Number.prototype.myRound = function (decimalPlaces) {
    var multiplier = Math.pow(10, decimalPlaces);

    return (Math.round(this * multiplier) / multiplier);
};
alert((239.525).myRound(2));

Mathematically alert should be 239.53 but its giving 239.52 as output. So i tried using .toFixed() function & i got proper answer.

But when i try to get answer for 239.575 it gives again wrong output.

alert((239.575).toFixed(2));

Here output should be 239.58 instead its giving 239.57.

This error creating a bit difference in final output. So can anyone help me to sort this out?

Answer 1

This method will give very correct round result.

function RoundNum(num, length) { 
    var number = Math.round(num * Math.pow(10, length)) / Math.pow(10, length);
    return number;
}

Just call this method.

alert(RoundNum(192.168,2));