JS实现千分位分隔符

function numFormat(num){

num = num.toString().split('.');

let arr = num[0].split('').reverse();

let res = [];

for(let i = 0; i < arr.length; ++i){

if(i%3 === 0 && i !== 0){

res.push(',')

}

res.push(arr[i])

}

res = res.reverse().join('');

if(num[1]){

res = res.concat('.' + num[1])

}

return res;

}

var a=1234567894532;

var b=673439.4542;

console.log(numFormat(a)); // "1,234,567,894,532"

console.log(numFormat(b)); // "673,439.4542"