Rounding

by timothyausten

JavaScript

// Add a better rounding method to Number.prototype
// http://stackoverflow.com/questions/7783543/javascript-convert-numbers-to-different-formats-or-string-alternative/7783771#7783771
// http://stackoverflow.com/questions/622374/extending-number-prototype-in-javascript-and-the-math-object
// Usage:
// (3.14592).round(2);
// Returns: 3.14

if (!Number.prototype.round) {
    Number.prototype.round = function (decimals) {
        if (typeof decimals === 'undefined') {
            decimals = 0;
        }
        return Math.round(
            this * Math.pow(10, decimals)
        ) / Math.pow(10, decimals);
    };
}


(function () {
    var pi = 3.141592,
        a = [],
        r = [
            'Normal rounding of 3.141592:',
            'pi.round(2): ' + pi.round(2),
            'pi.round(1): ' + pi.round(1),
            'pi.round(0): ' + pi.round(0),
            'Math.PI: ' + Math.PI,
            'Math.PI.round(2): ' + Math.PI.round(2),
            'With no parameter:',
            'pi.round(0): ' + pi.round(),
            'Backward rounding of 3141592:',
            '(pi * 100000).round(-1): ' + (pi * 100000).round(-1),
            '(pi * 100000).round(-2): ' + (pi * 100000).round(-2),
            '(pi * 100000).round(-3): ' + (pi * 100000).round(-3)
        ];

    for (var i = 0; i < r.length; i++) {
        a[i] = document.createElement('p');
        a[i].innerHTML = r[i];
        document.body.appendChild(a[i]);
    }
}());