js格式化数字

/**
 * 格式化number
 * @param num
 * @returns {String}
 */
function formatCurrency(num) {
	if (!num)
		return "0.00";
	num = num.toString().replace(/\$|\,/g, '');//去除$符号
	if (isNaN(num))
		num = "0.00";
	sign = (num == (num = Math.abs(num)));
	num = Math.floor(num * 100 + 0.50000000001);
	cents = num % 100;
	num = Math.floor(num / 100).toString();
	if (cents < 10)
		cents = "0" + cents;
	for ( var i = 0; i < Math.floor((num.length - (1 + i)) / 3); i++)
		num = num.substring(0, num.length - (4 * i + 3)) +  num.substring(num.length - (4 * i + 3));
	return (((sign) ? '' : '-') + '' + num + '.' + cents);
}