How to format number with commas and decimal in Javascript

For example, javascript format number comma

1234.542
and you want to format 1,234.54

You can use regular expression to solve the problem.

var value =1234.542
var parts = value.toFixed(2).split(".");
var num = parts[0].replace(/(\d)(?=(\d{3})+(?!\d))/g, "$1,") + 
    (parts[1] ? "." + parts[1] : "");

If you want result 1,234.542 then change toFixed(2) to toFixed(3)