Gaussian/banker’s rounding in JavaScript code example

Example: Gaussian/banker’s rounding in JavaScript

function roundIt(n, d = 0) {
            var m = Math.pow(10, d); 
            var n = +(d ? n * m : n).toFixed(8);
            var i = Math.floor(n), 
                diff = n - i; // getting the difference 
            var e = 1e-8; // Rounding errors in var(diff) 
            // Checking if the difference is less than or 
            // greater than, based on that adding the 1 to it. 
            var r = (diff > 0.5 - e && diff < 0.5 + e) ? 
                ((i % 2 == 0) ? i : i + 1) : Math.round(n);
            return d ? r / m : r; // if d != 0 then returning r/m else r 
}