技術積累系列(五)------前端js處理金額，添加千位分割符

自定義方法：

 function formatNumber(num) {
			if (!/^(\+|-)?(\d+)(\.\d+)?$/.test(num)) {
				return num;
			}
			var a = RegExp.$1, b = RegExp.$2, c = RegExp.$3;
			var re = new RegExp("(\\d)(\\d{3})(,|$)");
			while (re.test(b))   b = b.replace(re, "$1,$2$3");
			return a + "" + b + "" + c;
	    }