javascript thousand separator

1function numberWithCommas(x) {
2  return x.toString().replace(/\B(?=(\d{3})+(?!\d))/g, ',');
3}

1function numberWithCommas(x) {
2    return x.toString().replace(/\B(?<!\.\d*)(?=(\d{3})+(?!\d))/g, ",");
3}

1var number = 3500;
2
3console.log(new Intl.NumberFormat().format(number));
4// → '3,500' if in US English locale
5

1foramtNumber = (num,div=",")=>{
2  return num.toString().replace(/\B(?=(\d{3})+(?!\d))/g, div);
3
4}

1function numberWithCommas(x) {
2    return x.toString().replace(/\B(?=(\d{3})+(?!\d))/g, ",");
3}
4

1x.toString().toLocaleString(); // x must be a number