数字的千分位格式化方法

function toThousands(num) {
var result = [ ], counter = 0;
num = (num || 0).toString().split('');
for (var i = num.length - 1; i >= 0; i--) {
counter++;
result.unshift(num[i]);
if (!(counter % 3) && i != 0) {
result.unshift(',');
}
}
return result.join('');
}

function toThousands(num) {
var result = '', counter = 0;
num = (num || 0).toString();
for (var i = num.length - 1; i >= 0; i--) {
counter++;
result = num.charAt(i) + result;
if (!(counter % 3) && i != 0) {
result = ',' + result;
}
}
return result;
}

function toThousands(num) {
var num = (num || 0).toString(), result = '';
while (num.length > 3) {
result = ',' + num.slice(-3) + result;
num = num.slice(0, num.length - 3);
}
if (num) {
result = num + result;
}
return result;
}

function toThousands(num) {
return (num || 0).toString().replace(/(\d)(?=(?:\d{3})+$)/g, '$1,');
}

function toThousands(num) {
return (num || 0).toLocaleString('en-US');
}