Lobstrosity/commafy.1.js

## commafy.1.js
String.prototype.commafy = function () {
    return this.replace(
        /^(-?\d+)(\d{3}(\.\d+)?)$/,
        function (_, a, b) {
            return a.commafy() + ',' + b;
        }
    );
};

## commafy.2.js
Number.prototype.commafy = function () {
    return this.toString().commafy();
};

## commafy.stepThrough.1.js
'-1234567.89'.commafy()

## commafy.stepThrough.2.js
'-1234'.commafy() + ',' + '567.89'

## commafy.stepThrough.3.js
'-1'.commafy() + ',' + '234' + ',' + '567.89'

## commafy.stepThrough.4.js
'-1' + ',' + '234' + ',' + '567.89'

## commafy.stepThrough.5.js
'-1,234,567.89'
	String.prototype.commafy = function () {
	return this.replace(
	/^(-?\d+)(\d{3}(\.\d+)?)$/,
	function (_, a, b) {
	return a.commafy() + ',' + b;
	}
	);
	};
	Number.prototype.commafy = function () {
	return this.toString().commafy();
	};