js多位数字每隔三位加一个逗号

//每隔三位小数加逗号
function add_comma_toThousands(num) {
var num = (num || 0).toString();
var result = '';
while (num.length > 3) {
result = ',' + num.slice(-3) + result;
num = num.slice(0, num.length - 3);
}
if (num) { result = num + result; }
return result;
}